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# SPDX-License-Identifier: GPL-2.0+
#
# (C) Copyright 2000 - 2013
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
Summary:
========
This directory contains the source code for U-Boot, a boot loader for
Embedded boards based on PowerPC, ARM, MIPS and several other
processors, which can be installed in a boot ROM and used to
initialize and test the hardware or to download and run application
code.
The development of U-Boot is closely related to Linux: some parts of
the source code originate in the Linux source tree, we have some
header files in common, and special provision has been made to
support booting of Linux images.
Some attention has been paid to make this software easily
configurable and extendable. For instance, all monitor commands are
implemented with the same call interface, so that it's very easy to
add new commands. Also, instead of permanently adding rarely used
code (for instance hardware test utilities) to the monitor, you can
load and run it dynamically.
Status:
=======
In general, all boards for which a configuration option exists in the
Makefile have been tested to some extent and can be considered
"working". In fact, many of them are used in production systems.
In case of problems see the CHANGELOG file to find out who contributed
the specific port. In addition, there are various MAINTAINERS files
scattered throughout the U-Boot source identifying the people or
companies responsible for various boards and subsystems.
Note: As of August, 2010, there is no longer a CHANGELOG file in the
actual U-Boot source tree; however, it can be created dynamically
from the Git log using:
make CHANGELOG
Where to get help:
==================
In case you have questions about, problems with or contributions for
U-Boot, you should send a message to the U-Boot mailing list at
<u-boot@lists.denx.de>. There is also an archive of previous traffic
on the mailing list - please search the archive before asking FAQ's.
Please see https://lists.denx.de/pipermail/u-boot and
https://marc.info/?l=u-boot
Where to get source code:
=========================
The U-Boot source code is maintained in the Git repository at
https://source.denx.de/u-boot/u-boot.git ; you can browse it online at
https://source.denx.de/u-boot/u-boot
The "Tags" links on this page allow you to download tarballs of
any version you might be interested in. Official releases are also
available from the DENX file server through HTTPS or FTP.
https://ftp.denx.de/pub/u-boot/
ftp://ftp.denx.de/pub/u-boot/
Where we come from:
===================
- start from 8xxrom sources
- create PPCBoot project (https://sourceforge.net/projects/ppcboot)
- clean up code
- make it easier to add custom boards
- make it possible to add other [PowerPC] CPUs
- extend functions, especially:
* Provide extended interface to Linux boot loader
* S-Record download
* network boot
* ATA disk / SCSI ... boot
- create ARMBoot project (https://sourceforge.net/projects/armboot)
- add other CPU families (starting with ARM)
- create U-Boot project (https://sourceforge.net/projects/u-boot)
- current project page: see https://www.denx.de/wiki/U-Boot
Names and Spelling:
===================
The "official" name of this project is "Das U-Boot". The spelling
"U-Boot" shall be used in all written text (documentation, comments
in source files etc.). Example:
This is the README file for the U-Boot project.
File names etc. shall be based on the string "u-boot". Examples:
include/asm-ppc/u-boot.h
#include <asm/u-boot.h>
Variable names, preprocessor constants etc. shall be either based on
the string "u_boot" or on "U_BOOT". Example:
U_BOOT_VERSION u_boot_logo
IH_OS_U_BOOT u_boot_hush_start
Versioning:
===========
Starting with the release in October 2008, the names of the releases
were changed from numerical release numbers without deeper meaning
into a time stamp based numbering. Regular releases are identified by
names consisting of the calendar year and month of the release date.
Additional fields (if present) indicate release candidates or bug fix
releases in "stable" maintenance trees.
Examples:
U-Boot v2009.11 - Release November 2009
U-Boot v2009.11.1 - Release 1 in version November 2009 stable tree
U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
Directory Hierarchy:
====================
/arch Architecture-specific files
/arc Files generic to ARC architecture
/arm Files generic to ARM architecture
/m68k Files generic to m68k architecture
/microblaze Files generic to microblaze architecture
/mips Files generic to MIPS architecture
/nios2 Files generic to Altera NIOS2 architecture
/powerpc Files generic to PowerPC architecture
/riscv Files generic to RISC-V architecture
/sandbox Files generic to HW-independent "sandbox"
/sh Files generic to SH architecture
/x86 Files generic to x86 architecture
/xtensa Files generic to Xtensa architecture
/api Machine/arch-independent API for external apps
/board Board-dependent files
/boot Support for images and booting
/cmd U-Boot commands functions
/common Misc architecture-independent functions
/configs Board default configuration files
/disk Code for disk drive partition handling
/doc Documentation (a mix of ReST and READMEs)
/drivers Device drivers
/dts Makefile for building internal U-Boot fdt.
/env Environment support
/examples Example code for standalone applications, etc.
/fs Filesystem code (cramfs, ext2, jffs2, etc.)
/include Header Files
/lib Library routines generic to all architectures
/Licenses Various license files
/net Networking code
/post Power On Self Test
/scripts Various build scripts and Makefiles
/test Various unit test files
/tools Tools to build and sign FIT images, etc.
Software Configuration:
=======================
Selection of Processor Architecture and Board Type:
---------------------------------------------------
For all supported boards there are ready-to-use default
configurations available; just type "make <board_name>_defconfig".
Example: For a TQM823L module type:
cd u-boot
make TQM823L_defconfig
Note: If you're looking for the default configuration file for a board
you're sure used to be there but is now missing, check the file
doc/README.scrapyard for a list of no longer supported boards.
Sandbox Environment:
--------------------
U-Boot can be built natively to run on a Linux host using the 'sandbox'
board. This allows feature development which is not board- or architecture-
specific to be undertaken on a native platform. The sandbox is also used to
run some of U-Boot's tests.
See doc/arch/sandbox.rst for more details.
Board Initialisation Flow:
--------------------------
This is the intended start-up flow for boards. This should apply for both
SPL and U-Boot proper (i.e. they both follow the same rules).
Note: "SPL" stands for "Secondary Program Loader," which is explained in
more detail later in this file.
At present, SPL mostly uses a separate code path, but the function names
and roles of each function are the same. Some boards or architectures
may not conform to this. At least most ARM boards which use
CONFIG_SPL_FRAMEWORK conform to this.
Execution typically starts with an architecture-specific (and possibly
CPU-specific) start.S file, such as:
- arch/arm/cpu/armv7/start.S
- arch/powerpc/cpu/mpc83xx/start.S
- arch/mips/cpu/start.S
and so on. From there, three functions are called; the purpose and
limitations of each of these functions are described below.
lowlevel_init():
- purpose: essential init to permit execution to reach board_init_f()
- no global_data or BSS
- there is no stack (ARMv7 may have one but it will soon be removed)
- must not set up SDRAM or use console
- must only do the bare minimum to allow execution to continue to
board_init_f()
- this is almost never needed
- return normally from this function
board_init_f():
- purpose: set up the machine ready for running board_init_r():
i.e. SDRAM and serial UART
- global_data is available
- stack is in SRAM
- BSS is not available, so you cannot use global/static variables,
only stack variables and global_data
Non-SPL-specific notes:
- dram_init() is called to set up DRAM. If already done in SPL this
can do nothing
SPL-specific notes:
- you can override the entire board_init_f() function with your own
version as needed.
- preloader_console_init() can be called here in extremis
- should set up SDRAM, and anything needed to make the UART work
- there is no need to clear BSS, it will be done by crt0.S
- for specific scenarios on certain architectures an early BSS *can*
be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
of BSS prior to entering board_init_f()) but doing so is discouraged.
Instead it is strongly recommended to architect any code changes
or additions such to not depend on the availability of BSS during
board_init_f() as indicated in other sections of this README to
maintain compatibility and consistency across the entire code base.
- must return normally from this function (don't call board_init_r()
directly)
Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
this point the stack and global_data are relocated to below
CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
memory.
board_init_r():
- purpose: main execution, common code
- global_data is available
- SDRAM is available
- BSS is available, all static/global variables can be used
- execution eventually continues to main_loop()
Non-SPL-specific notes:
- U-Boot is relocated to the top of memory and is now running from
there.
SPL-specific notes:
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
CONFIG_SYS_FSL_HAS_CCI400
Defined For SoC that has cache coherent interconnect
CCN-400
CONFIG_SYS_FSL_HAS_CCN504
Defined for SoC that has cache coherent interconnect CCN-504
The following options need to be configured:
- CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.
- Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.
- 85xx CPU Options:
CONFIG_SYS_PPC64
Specifies that the core is a 64-bit PowerPC implementation (implements
the "64" category of the Power ISA). This is necessary for ePAPR
compliance, among other possible reasons.
CONFIG_SYS_FSL_ERRATUM_A004510
Enables a workaround for erratum A004510. If set,
then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
Defines one or two SoC revisions (low 8 bits of SVR)
for which the A004510 workaround should be applied.
The rest of SVR is either not relevant to the decision
of whether the erratum is present (e.g. p2040 versus
p2041) or is implied by the build target, which controls
whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
See Freescale App Note 4493 for more information about
this erratum.
CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
This is the value to write into CCSR offset 0x18600
according to the A004510 workaround.
CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
Single Source Clock is clocking mode present in some of FSL SoC's.
In this mode, a single differential clock is used to supply
clocks to the sysclock, ddrclock and usbclock.
- Generic CPU options:
CONFIG_SYS_FSL_DDR
Freescale DDR driver in use. This type of DDR controller is
found in mpc83xx, mpc85xx as well as some ARM core SoCs.
CONFIG_SYS_FSL_DDR_ADDR
Freescale DDR memory-mapped register base.
CONFIG_SYS_FSL_IFC_CLK_DIV
Defines divider of platform clock(clock input to IFC controller).
CONFIG_SYS_FSL_LBC_CLK_DIV
Defines divider of platform clock(clock input to eLBC controller).
CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
Physical address from the view of DDR controllers. It is the
same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
it could be different for ARM SoCs.
- MIPS CPU options:
CONFIG_XWAY_SWAP_BYTES
Enable compilation of tools/xway-swap-bytes needed for Lantiq
XWAY SoCs for booting from NOR flash. The U-Boot image needs to
be swapped if a flash programmer is used.
- ARM options:
CONFIG_SYS_EXCEPTION_VECTORS_HIGH
Select high exception vectors of the ARM core, e.g., do not
clear the V bit of the c1 register of CP15.
COUNTER_FREQUENCY
Generic timer clock source frequency.
COUNTER_FREQUENCY_REAL
Generic timer clock source frequency if the real clock is
different from COUNTER_FREQUENCY, and can only be determined
at run time.
- Tegra SoC options:
CONFIG_TEGRA_SUPPORT_NON_SECURE
Support executing U-Boot in non-secure (NS) mode. Certain
impossible actions will be skipped if the CPU is in NS mode,
such as ARM architectural timer initialization.
- Linux Kernel Interface:
CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
When transferring memsize parameter to Linux, some versions
expect it to be in bytes, others in MB.
Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
CONFIG_OF_LIBFDT
New kernel versions are expecting firmware settings to be
passed using flattened device trees (based on open firmware
concepts).
CONFIG_OF_LIBFDT
* New libfdt-based support
* Adds the "fdt" command
* The bootm command automatically updates the fdt
OF_TBCLK - The timebase frequency.
boards with QUICC Engines require OF_QE to set UCC MAC
addresses
CONFIG_OF_IDE_FIXUP
U-Boot can detect if an IDE device is present or not.
If not, and this new config option is activated, U-Boot
removes the ATA node from the DTS before booting Linux,
so the Linux IDE driver does not probe the device and
crash. This is needed for buggy hardware (uc101) where
no pull down resistor is connected to the signal IDE5V_DD7.
- vxWorks boot parameters:
bootvx constructs a valid bootline using the following
environments variables: bootdev, bootfile, ipaddr, netmask,
serverip, gatewayip, hostname, othbootargs.
It loads the vxWorks image pointed bootfile.
Note: If a "bootargs" environment is defined, it will override
the defaults discussed just above.
- Cache Configuration for ARM:
CONFIG_SYS_PL310_BASE - Physical base address of PL310
controller register space
- Serial Ports:
CONFIG_PL011_CLOCK
If you have Amba PrimeCell PL011 UARTs, set this variable to
the clock speed of the UARTs.
CONFIG_PL01x_PORTS
If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
define this to a list of base addresses for each (supported)
port. See e.g. include/configs/versatile.h
CONFIG_SERIAL_HW_FLOW_CONTROL
Define this variable to enable hw flow control in serial driver.
Current user of this option is drivers/serial/nsl16550.c driver
- Removal of commands
If no commands are needed to boot, you can disable
CONFIG_CMDLINE to remove them. In this case, the command line
will not be available, and when U-Boot wants to execute the
boot command (on start-up) it will call board_run_command()
instead. This can reduce image size significantly for very
simple boot procedures.
- Regular expression support:
CONFIG_REGEX
If this variable is defined, U-Boot is linked against
the SLRE (Super Light Regular Expression) library,
which adds regex support to some commands, as for
example "env grep" and "setexpr".
- Watchdog:
CONFIG_SYS_WATCHDOG_FREQ
Some platforms automatically call WATCHDOG_RESET()
from the timer interrupt handler every
CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
board configuration file, a default of CONFIG_SYS_HZ/2
(i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
to 0 disables calling WATCHDOG_RESET() from the timer
interrupt.
- Real-Time Clock:
When CONFIG_CMD_DATE is selected, the type of the RTC
has to be selected, too. Define exactly one of the
following options:
CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
CONFIG_RTC_MC146818 - use MC146818 RTC
CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
CONFIG_RTC_DS164x - use Dallas DS164x RTC
CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
CONFIG_SYS_RV3029_TCR - enable trickle charger on
RV3029 RTC.
Note that if the RTC uses I2C, then the I2C interface
must also be configured. See I2C Support, below.
- GPIO Support:
CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
chip-ngpio pairs that tell the PCA953X driver the number of
pins supported by a particular chip.
Note that if the GPIO device uses I2C, then the I2C interface
must also be configured. See I2C Support, below.
- I/O tracing:
When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
accesses and can checksum them or write a list of them out
to memory. See the 'iotrace' command for details. This is
useful for testing device drivers since it can confirm that
the driver behaves the same way before and after a code
change. Currently this is supported on sandbox and arm. To
add support for your architecture, add '#include <iotrace.h>'
to the bottom of arch/<arch>/include/asm/io.h and test.
Example output from the 'iotrace stats' command is below.
Note that if the trace buffer is exhausted, the checksum will
still continue to operate.
iotrace is enabled
Start: 10000000 (buffer start address)
Size: 00010000 (buffer size)
Offset: 00000120 (current buffer offset)
Output: 10000120 (start + offset)
Count: 00000018 (number of trace records)
CRC32: 9526fb66 (CRC32 of all trace records)
- Timestamp Support:
When CONFIG_TIMESTAMP is selected, the timestamp
(date and time) of an image is printed by image
commands like bootm or iminfo. This option is
automatically enabled when you select CONFIG_CMD_DATE .
- Partition Labels (disklabels) Supported:
Zero or more of the following:
CONFIG_MAC_PARTITION Apple's MacOS partition table.
CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
bootloader. Note 2TB partition limit; see
disk/part_efi.c
CONFIG_SCSI) you must configure support for at
least one non-MTD partition type as well.
- NETWORK Support (PCI):
CONFIG_E1000_SPI
Utility code for direct access to the SPI bus on Intel 8257x.
This does not do anything useful unless you set at least one
of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
CONFIG_NATSEMI
Support for National dp83815 chips.
CONFIG_NS8382X
Support for National dp8382[01] gigabit chips.
- NETWORK Support (other):
CONFIG_CALXEDA_XGMAC
Support for the Calxeda XGMAC device
CONFIG_LAN91C96
Support for SMSC's LAN91C96 chips.
CONFIG_LAN91C96_USE_32_BIT
Define this to enable 32 bit addressing
CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
Define this if you have more then 3 PHYs.
CONFIG_FTGMAC100
Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
CONFIG_FTGMAC100_EGIGA
Define this to use GE link update with gigabit PHY.
Define this if FTGMAC100 is connected to gigabit PHY.
If your system has 10/100 PHY only, it might not occur
wrong behavior. Because PHY usually return timeout or
useless data when polling gigabit status and gigabit
control registers. This behavior won't affect the
correctnessof 10/100 link speed update.
CONFIG_SH_ETHER
Support for Renesas on-chip Ethernet controller
CONFIG_SH_ETHER_USE_PORT
Define the number of ports to be used
CONFIG_SH_ETHER_PHY_ADDR
Define the ETH PHY's address
CONFIG_SH_ETHER_CACHE_WRITEBACK
If this option is set, the driver enables cache flush.
- TPM Support:
CONFIG_TPM
Support TPM devices.
CONFIG_TPM_TIS_INFINEON
Support for Infineon i2c bus TPM devices. Only one device
per system is supported at this time.
CONFIG_TPM_TIS_I2C_BURST_LIMITATION
Define the burst count bytes upper limit
CONFIG_TPM_ST33ZP24
Support for STMicroelectronics TPM devices. Requires DM_TPM support.
CONFIG_TPM_ST33ZP24_I2C
Support for STMicroelectronics ST33ZP24 I2C devices.
Requires TPM_ST33ZP24 and I2C.
CONFIG_TPM_ST33ZP24_SPI
Support for STMicroelectronics ST33ZP24 SPI devices.
Requires TPM_ST33ZP24 and SPI.
CONFIG_TPM_ATMEL_TWI
Support for Atmel TWI TPM device. Requires I2C support.
CONFIG_TPM_TIS_LPC
Support for generic parallel port TPM devices. Only one device
per system is supported at this time.
CONFIG_TPM_TIS_BASE_ADDRESS
Base address where the generic TPM device is mapped
to. Contemporary x86 systems usually map it at
0xfed40000.
CONFIG_TPM
Define this to enable the TPM support library which provides
functional interfaces to some TPM commands.
Requires support for a TPM device.
CONFIG_TPM_AUTH_SESSIONS
Define this to enable authorized functions in the TPM library.
Requires CONFIG_TPM and CONFIG_SHA1.
- USB Support:
At the moment only the UHCI host controller is
supported (PIP405, MIP405); define
CONFIG_USB_UHCI to enable it.
define CONFIG_USB_KEYBOARD to enable the USB Keyboard
and define CONFIG_USB_STORAGE to enable the USB
storage devices.
Note:
Supported are USB Keyboards and USB Floppy drives
(TEAC FD-05PUB).
CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
HW module registers.
- USB Device:
Define the below if you wish to use the USB console.
Once firmware is rebuilt from a serial console issue the
command "setenv stdin usbtty; setenv stdout usbtty" and
attach your USB cable. The Unix command "dmesg" should print
it has found a new device. The environment variable usbtty
can be set to gserial or cdc_acm to enable your device to
appear to a USB host as a Linux gserial device or a
Common Device Class Abstract Control Model serial device.
If you select usbtty = gserial you should be able to enumerate
a Linux host by
# modprobe usbserial vendor=0xVendorID product=0xProductID
else if using cdc_acm, simply setting the environment
variable usbtty to be cdc_acm should suffice. The following
might be defined in YourBoardName.h
CONFIG_USB_DEVICE
Define this to build a UDC device
CONFIG_USB_TTY
Define this to have a tty type of device available to
talk to the UDC device
CONFIG_USBD_HS
Define this to enable the high speed support for usb
device and usbtty. If this feature is enabled, a routine
int is_usbd_high_speed(void)
also needs to be defined by the driver to dynamically poll
whether the enumeration has succeded at high speed or full
speed.
If you have a USB-IF assigned VendorID then you may wish to
define your own vendor specific values either in BoardName.h
or directly in usbd_vendor_info.h. If you don't define
CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
should pretend to be a Linux device to it's target host.
CONFIG_USBD_MANUFACTURER
Define this string as the name of your company for
- CONFIG_USBD_MANUFACTURER "my company"
CONFIG_USBD_PRODUCT_NAME
Define this string as the name of your product
- CONFIG_USBD_PRODUCT_NAME "acme usb device"
CONFIG_USBD_VENDORID
Define this as your assigned Vendor ID from the USB
Implementors Forum. This *must* be a genuine Vendor ID
to avoid polluting the USB namespace.
- CONFIG_USBD_VENDORID 0xFFFF
CONFIG_USBD_PRODUCTID
Define this as the unique Product ID
for your device
- CONFIG_USBD_PRODUCTID 0xFFFF
- ULPI Layer Support:
The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
the generic ULPI layer. The generic layer accesses the ULPI PHY
via the platform viewport, so you need both the genric layer and
the viewport enabled. Currently only Chipidea/ARC based
viewport is supported.
To enable the ULPI layer support, define CONFIG_USB_ULPI and
CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
If your ULPI phy needs a different reference clock than the
standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
the appropriate value in Hz.
- MMC Support:
CONFIG_SH_MMCIF
Support for Renesas on-chip MMCIF controller
CONFIG_SH_MMCIF_ADDR
Define the base address of MMCIF registers
CONFIG_SH_MMCIF_CLK
Define the clock frequency for MMCIF
- USB Device Firmware Update (DFU) class support:
CONFIG_DFU_OVER_USB
This enables the USB portion of the DFU USB class
CONFIG_DFU_NAND
This enables support for exposing NAND devices via DFU.
CONFIG_DFU_RAM
This enables support for exposing RAM via DFU.
Note: DFU spec refer to non-volatile memory usage, but
allow usages beyond the scope of spec - here RAM usage,
one that would help mostly the developer.
CONFIG_SYS_DFU_DATA_BUF_SIZE
Dfu transfer uses a buffer before writing data to the
raw storage device. Make the size (in bytes) of this buffer
configurable. The size of this buffer is also configurable
through the "dfu_bufsiz" environment variable.
CONFIG_SYS_DFU_MAX_FILE_SIZE
When updating files rather than the raw storage device,
we use a static buffer to copy the file into and then write
the buffer once we've been given the whole file. Define
this to the maximum filesize (in bytes) for the buffer.
Default is 4 MiB if undefined.
DFU_DEFAULT_POLL_TIMEOUT
Poll timeout [ms], is the timeout a device can send to the
host. The host must wait for this timeout before sending
a subsequent DFU_GET_STATUS request to the device.
DFU_MANIFEST_POLL_TIMEOUT
Poll timeout [ms], which the device sends to the host when
entering dfuMANIFEST state. Host waits this timeout, before
sending again an USB request to the device.
- Keyboard Support:
See Kconfig help for available keyboard drivers.
- MII/PHY support:
CONFIG_PHY_CLOCK_FREQ (ppc4xx)
The clock frequency of the MII bus
CONFIG_PHY_CMD_DELAY (ppc4xx)
Some PHY like Intel LXT971A need extra delay after
command issued before MII status register can be read
- IP address:
CONFIG_IPADDR
Define a default value for the IP address to use for
the default Ethernet interface, in case this is not
determined through e.g. bootp.
(Environment variable "ipaddr")
- Server IP address:
CONFIG_SERVERIP
Defines a default value for the IP address of a TFTP
server to contact when using the "tftboot" command.
(Environment variable "serverip")
- Gateway IP address:
CONFIG_GATEWAYIP
Defines a default value for the IP address of the
default router where packets to other networks are
sent to.
(Environment variable "gatewayip")
- Subnet mask:
CONFIG_NETMASK
Defines a default value for the subnet mask (or
routing prefix) which is used to determine if an IP
address belongs to the local subnet or needs to be
forwarded through a router.
(Environment variable "netmask")
- BOOTP Recovery Mode:
CONFIG_BOOTP_RANDOM_DELAY
If you have many targets in a network that try to
boot using BOOTP, you may want to avoid that all
systems send out BOOTP requests at precisely the same
moment (which would happen for instance at recovery
from a power failure, when all systems will try to
boot, thus flooding the BOOTP server. Defining
CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
inserted before sending out BOOTP requests. The
following delays are inserted then:
1st BOOTP request: delay 0 ... 1 sec
2nd BOOTP request: delay 0 ... 2 sec
3rd BOOTP request: delay 0 ... 4 sec
4th and following
BOOTP requests: delay 0 ... 8 sec
CONFIG_BOOTP_ID_CACHE_SIZE
BOOTP packets are uniquely identified using a 32-bit ID. The
server will copy the ID from client requests to responses and
U-Boot will use this to determine if it is the destination of
an incoming response. Some servers will check that addresses
aren't in use before handing them out (usually using an ARP
ping) and therefore take up to a few hundred milliseconds to
respond. Network congestion may also influence the time it
takes for a response to make it back to the client. If that
time is too long, U-Boot will retransmit requests. In order
to allow earlier responses to still be accepted after these
retransmissions, U-Boot's BOOTP client keeps a small cache of
IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
cache. The default is to keep IDs for up to four outstanding
requests. Increasing this will allow U-Boot to accept offers
from a BOOTP client in networks with unusually high latency.
- DHCP Advanced Options:
- Link-local IP address negotiation:
Negotiate with other link-local clients on the local network
for an address that doesn't require explicit configuration.
This is especially useful if a DHCP server cannot be guaranteed
to exist in all environments that the device must operate.
See doc/README.link-local for more information.
- MAC address from environment variables
FDT_SEQ_MACADDR_FROM_ENV
Fix-up device tree with MAC addresses fetched sequentially from
environment variables. This config work on assumption that
non-usable ethernet node of device-tree are either not present
or their status has been marked as "disabled".
- CDP Options:
CONFIG_CDP_DEVICE_ID
The device id used in CDP trigger frames.
CONFIG_CDP_DEVICE_ID_PREFIX
A two character string which is prefixed to the MAC address
of the device.
CONFIG_CDP_PORT_ID
A printf format string which contains the ascii name of
the port. Normally is set to "eth%d" which sets
eth0 for the first Ethernet, eth1 for the second etc.
CONFIG_CDP_CAPABILITIES
A 32bit integer which indicates the device capabilities;
0x00000010 for a normal host which does not forwards.
CONFIG_CDP_VERSION
An ascii string containing the version of the software.
CONFIG_CDP_PLATFORM
An ascii string containing the name of the platform.
CONFIG_CDP_TRIGGER
A 32bit integer sent on the trigger.
CONFIG_CDP_POWER_CONSUMPTION
A 16bit integer containing the power consumption of the
device in .1 of milliwatts.
CONFIG_CDP_APPLIANCE_VLAN_TYPE
A byte containing the id of the VLAN.
- Status LED: CONFIG_LED_STATUS
Several configurations allow to display the current
status using a LED. For instance, the LED will blink
fast while running U-Boot code, stop blinking as
soon as a reply to a BOOTP request was received, and
start blinking slow once the Linux kernel is running
(supported by a status LED driver in the Linux
kernel). Defining CONFIG_LED_STATUS enables this
feature in U-Boot.
Additional options:
CONFIG_LED_STATUS_GPIO
The status LED can be connected to a GPIO pin.
In such cases, the gpio_led driver can be used as a
status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
to include the gpio_led driver in the U-Boot binary.
CONFIG_GPIO_LED_INVERTED_TABLE
Some GPIO connected LEDs may have inverted polarity in which
case the GPIO high value corresponds to LED off state and
GPIO low value corresponds to LED on state.
In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
with a list of GPIO LEDs that have inverted polarity.
- I2C Support:
CONFIG_SYS_NUM_I2C_BUSES
Hold the number of i2c buses you want to use.
CONFIG_SYS_I2C_DIRECT_BUS
define this, if you don't use i2c muxes on your hardware.
if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
omit this define.
CONFIG_SYS_I2C_MAX_HOPS
define how many muxes are maximal consecutively connected
on one i2c bus. If you not use i2c muxes, omit this
define.
CONFIG_SYS_I2C_BUSES
hold a list of buses you want to use, only used if
CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
CONFIG_SYS_NUM_I2C_BUSES = 9:
CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
{1, {I2C_NULL_HOP}}, \
{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
}
which defines
bus 0 on adapter 0 without a mux
bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
bus 6 on adapter 1 without a mux
bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
If you do not have i2c muxes on your board, omit this define.
- Legacy I2C Support:
If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
then the following macros need to be defined (examples are
from include/configs/lwmon.h):
I2C_INIT
(Optional). Any commands necessary to enable the I2C
controller or configure ports.
eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
I2C_ACTIVE
The code necessary to make the I2C data line active
(driven). If the data line is open collector, this
define can be null.
eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
I2C_TRISTATE
The code necessary to make the I2C data line tri-stated
(inactive). If the data line is open collector, this
define can be null.
eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
I2C_READ
Code that returns true if the I2C data line is high,
false if it is low.
eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
I2C_SDA(bit)
If <bit> is true, sets the I2C data line high. If it
is false, it clears it (low).
eg: #define I2C_SDA(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
else immr->im_cpm.cp_pbdat &= ~PB_SDA
I2C_SCL(bit)
If <bit> is true, sets the I2C clock line high. If it
is false, it clears it (low).
eg: #define I2C_SCL(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
else immr->im_cpm.cp_pbdat &= ~PB_SCL
I2C_DELAY
This delay is invoked four times per clock cycle so this
controls the rate of data transfer. The data rate thus
is 1 / (I2C_DELAY * 4). Often defined to be something
like:
#define I2C_DELAY udelay(2)
CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
If your arch supports the generic GPIO framework (asm/gpio.h),
then you may alternatively define the two GPIOs that are to be
used as SCL / SDA. Any of the previous I2C_xxx macros will
have GPIO-based defaults assigned to them as appropriate.
You should define these to the GPIO value as given directly to
the generic GPIO functions.
CONFIG_I2C_MULTI_BUS
This option allows the use of multiple I2C buses, each of which
must have a controller. At any point in time, only one bus is
active. To switch to a different bus, use the 'i2c dev' command.
Note that bus numbering is zero-based.
CONFIG_SYS_I2C_NOPROBES
This option specifies a list of I2C devices that will be skipped
when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
is set, specify a list of bus-device pairs. Otherwise, specify
a 1D array of device addresses
e.g.
#undef CONFIG_I2C_MULTI_BUS
#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
will skip addresses 0x50 and 0x68 on a board with one I2C bus
#define CONFIG_I2C_MULTI_BUS
#define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
CONFIG_SYS_RTC_BUS_NUM
If defined, then this indicates the I2C bus number for the RTC.
If not defined, then U-Boot assumes that RTC is on I2C bus 0.
CONFIG_SOFT_I2C_READ_REPEATED_START
defining this will force the i2c_read() function in
the soft_i2c driver to perform an I2C repeated start
between writing the address pointer and reading the
data. If this define is omitted the default behaviour
of doing a stop-start sequence will be used. Most I2C
devices can use either method, but some require one or
the other.
- SPI Support: CONFIG_SPI
Enables SPI driver (so far only tested with
SPI EEPROM, also an instance works with Crystal A/D and
D/As on the SACSng board)
CONFIG_SYS_SPI_MXC_WAIT
Timeout for waiting until spi transfer completed.
default: (CONFIG_SYS_HZ/100) /* 10 ms */
- FPGA Support: CONFIG_FPGA
Enables FPGA subsystem.
CONFIG_FPGA_<vendor>
Enables support for specific chip vendors.
(ALTERA, XILINX)
CONFIG_FPGA_<family>
Enables support for FPGA family.
(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
CONFIG_SYS_FPGA_CHECK_BUSY
Enable checks on FPGA configuration interface busy
status by the configuration function. This option
will require a board or device specific function to
be written.
CONFIG_FPGA_DELAY
If defined, a function that provides delays in the FPGA
configuration driver.
CONFIG_SYS_FPGA_CHECK_ERROR
Check for configuration errors during FPGA bitfile
loading. For example, abort during Virtex II
configuration if the INIT_B line goes low (which
indicated a CRC error).
CONFIG_SYS_FPGA_WAIT_INIT
Maximum time to wait for the INIT_B line to de-assert
after PROB_B has been de-asserted during a Virtex II
FPGA configuration sequence. The default time is 500
ms.
CONFIG_SYS_FPGA_WAIT_BUSY
Maximum time to wait for BUSY to de-assert during
Virtex II FPGA configuration. The default is 5 ms.
CONFIG_SYS_FPGA_WAIT_CONFIG
Time to wait after FPGA configuration. The default is
200 ms.
- Vendor Parameter Protection:
U-Boot considers the values of the environment
variables "serial#" (Board Serial Number) and
"ethaddr" (Ethernet Address) to be parameters that
are set once by the board vendor / manufacturer, and
protects these variables from casual modification by
the user. Once set, these variables are read-only,
and write or delete attempts are rejected. You can
change this behaviour:
If CONFIG_ENV_OVERWRITE is #defined in your config
file, the write protection for vendor parameters is
completely disabled. Anybody can change or delete
these parameters.
Alternatively, if you define _both_ an ethaddr in the
default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
Ethernet address is installed in the environment,
which can be changed exactly ONCE by the user. [The
serial# is unaffected by this, i. e. it remains
read-only.]
The same can be accomplished in a more flexible way
for any variable by configuring the type of access
to allow for those variables in the ".flags" variable
or define CONFIG_ENV_FLAGS_LIST_STATIC.
- Protected RAM:
CONFIG_PRAM
Define this variable to enable the reservation of
"protected RAM", i. e. RAM which is not overwritten
by U-Boot. Define CONFIG_PRAM to hold the number of
kB you want to reserve for pRAM. You can overwrite
this default value by defining an environment
variable "pram" to the number of kB you want to
reserve. Note that the board info structure will
still show the full amount of RAM. If pRAM is
reserved, a new environment variable "mem" will
automatically be defined to hold the amount of
remaining RAM in a form that can be passed as boot
argument to Linux, for instance like that:
setenv bootargs ... mem=\${mem}
saveenv
This way you can tell Linux not to use this memory,
either, which results in a memory region that will
not be affected by reboots.
*WARNING* If your board configuration uses automatic
detection of the RAM size, you must make sure that
this memory test is non-destructive. So far, the
following board configurations are known to be
"pRAM-clean":
IVMS8, IVML24, SPD8xx,
HERMES, IP860, RPXlite, LWMON,
FLAGADM
- Error Recovery:
Note:
In the current implementation, the local variables
space and global environment variables space are
separated. Local variables are those you define by
simply typing `name=value'. To access a local
variable later on, you have write `$name' or
`${name}'; to execute the contents of a variable
directly type `$name' at the command prompt.
Global environment variables are those you use
setenv/printenv to work with. To run a command stored
in such a variable, you need to use the run command,
and you must not use the '$' sign to access them.
To store commands and special characters in a
variable, please use double quotation marks
surrounding the whole text of the variable, instead
of the backslashes before semicolons and special
symbols.
- Default Environment:
CONFIG_EXTRA_ENV_SETTINGS
Define this to contain any number of null terminated
strings (variable = value pairs) that will be part of
the default environment compiled into the boot image.
For example, place something like this in your
board's config file:
#define CONFIG_EXTRA_ENV_SETTINGS \
"myvar1=value1\0" \
"myvar2=value2\0"
Warning: This method is based on knowledge about the
internal format how the environment is stored by the
U-Boot code. This is NOT an official, exported
interface! Although it is unlikely that this format
will change soon, there is no guarantee either.
You better know what you are doing here.
Note: overly (ab)use of the default environment is
discouraged. Make sure to check other ways to preset
the environment like the "source" command or the
boot command first.
CONFIG_DELAY_ENVIRONMENT
Normally the environment is loaded when the board is
initialised so that it is available to U-Boot. This inhibits
that so that the environment is not available until
explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
this is instead controlled by the value of
/config/load-environment.
CONFIG_STANDALONE_LOAD_ADDR
This option defines a board specific value for the
address where standalone program gets loaded, thus
overwriting the architecture dependent default
settings.
- Automatic software updates via TFTP server
CONFIG_UPDATE_TFTP
CONFIG_UPDATE_TFTP_CNT_MAX
CONFIG_UPDATE_TFTP_MSEC_MAX
These options enable and control the auto-update feature;
for a more detailed description refer to doc/README.update.
- MTD Support (mtdparts command, UBI support)
CONFIG_MTD_UBI_WL_THRESHOLD
This parameter defines the maximum difference between the highest
erase counter value and the lowest erase counter value of eraseblocks
of UBI devices. When this threshold is exceeded, UBI starts performing
wear leveling by means of moving data from eraseblock with low erase
counter to eraseblocks with high erase counter.
The default value should be OK for SLC NAND flashes, NOR flashes and
other flashes which have eraseblock life-cycle 100000 or more.
However, in case of MLC NAND flashes which typically have eraseblock
life-cycle less than 10000, the threshold should be lessened (e.g.,
to 128 or 256, although it does not have to be power of 2).
default: 4096
CONFIG_MTD_UBI_BEB_LIMIT
This option specifies the maximum bad physical eraseblocks UBI
expects on the MTD device (per 1024 eraseblocks). If the
underlying flash does not admit of bad eraseblocks (e.g. NOR
flash), this value is ignored.
NAND datasheets often specify the minimum and maximum NVM
(Number of Valid Blocks) for the flashes' endurance lifetime.
The maximum expected bad eraseblocks per 1024 eraseblocks
then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
which gives 20 for most NANDs (MaxNVB is basically the total
count of eraseblocks on the chip).
To put it differently, if this value is 20, UBI will try to
reserve about 1.9% of physical eraseblocks for bad blocks
handling. And that will be 1.9% of eraseblocks on the entire
NAND chip, not just the MTD partition UBI attaches. This means
that if you have, say, a NAND flash chip admits maximum 40 bad
eraseblocks, and it is split on two MTD partitions of the same
size, UBI will reserve 40 eraseblocks when attaching a
partition.
default: 20
CONFIG_MTD_UBI_FASTMAP
Fastmap is a mechanism which allows attaching an UBI device
in nearly constant time. Instead of scanning the whole MTD device it
only has to locate a checkpoint (called fastmap) on the device.
The on-flash fastmap contains all information needed to attach
the device. Using fastmap makes only sense on large devices where
attaching by scanning takes long. UBI will not automatically install
a fastmap on old images, but you can set the UBI parameter
CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
that fastmap-enabled images are still usable with UBI implementations
without fastmap support. On typical flash devices the whole fastmap
fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
Set this parameter to enable fastmap automatically on images
without a fastmap.
default: 0
CONFIG_MTD_UBI_FM_DEBUG
Enable UBI fastmap debug
default: 0
- SPL framework
CONFIG_SPL
Enable building of SPL globally.
CONFIG_SPL_PANIC_ON_RAW_IMAGE
When defined, SPL will panic() if the image it has
loaded does not have a signature.
Defining this is useful when code which loads images
in SPL cannot guarantee that absolutely all read errors
will be caught.
An example is the LPC32XX MLC NAND driver, which will
consider that a completely unreadable NAND block is bad,
and thus should be skipped silently.
CONFIG_SPL_DISPLAY_PRINT
For ARM, enable an optional function to print more information
about the running system.
CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
Set this for NAND SPL on PPC mpc83xx targets, so that
start.S waits for the rest of the SPL to load before
continuing (the hardware starts execution after just
loading the first page rather than the full 4K).
CONFIG_SPL_UBI
Support for a lightweight UBI (fastmap) scanner and
loader
CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
CONFIG_SYS_NAND_ECCBYTES
Defines the size and behavior of the NAND that SPL uses
to read U-Boot
CONFIG_SYS_NAND_U_BOOT_DST
Location in memory to load U-Boot to
CONFIG_SYS_NAND_U_BOOT_SIZE
Size of image to load
CONFIG_SYS_NAND_U_BOOT_START
Entry point in loaded image to jump to
CONFIG_SYS_NAND_HW_ECC_OOBFIRST
Define this if you need to first read the OOB and then the
data. This is used, for example, on davinci platforms.
CONFIG_SPL_RAM_DEVICE
Support for running image already present in ram, in SPL binary
CONFIG_SPL_FIT_PRINT
Printing information about a FIT image adds quite a bit of
code to SPL. So this is normally disabled in SPL. Use this
option to re-enable it. This will affect the output of the
bootm command when booting a FIT image.
- Interrupt support (PPC):
There are common interrupt_init() and timer_interrupt()
for all PPC archs. interrupt_init() calls interrupt_init_cpu()
for CPU specific initialization. interrupt_init_cpu()
should set decrementer_count to appropriate value. If
CPU resets decrementer automatically after interrupt
(ppc4xx) it should set decrementer_count to zero.
timer_interrupt() calls timer_interrupt_cpu() for CPU
specific handling. If board has watchdog / status_led
/ other_activity_monitor it works automatically from
general timer_interrupt().
Board initialization settings:
------------------------------
During Initialization u-boot calls a number of board specific functions
to allow the preparation of board specific prerequisites, e.g. pin setup
before drivers are initialized. To enable these callbacks the
following configuration macros have to be defined. Currently this is
architecture specific, so please check arch/your_architecture/lib/board.c
typically in board_init_f() and board_init_r().
- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
- CONFIG_BOARD_LATE_INIT: Call board_late_init()
Configuration Settings:
-----------------------
- MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
Optionally it can be defined to support 64-bit memory commands.
- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
undefine this when you're short of memory.
- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
width of the commands listed in the 'help' command output.
- CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
prompt for user input.
- CONFIG_SYS_BAUDRATE_TABLE:
List of legal baudrate settings for this board.
- CONFIG_SYS_MEM_RESERVE_SECURE
Only implemented for ARMv8 for now.
If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
is substracted from total RAM and won't be reported to OS.
This memory can be used as secure memory. A variable
gd->arch.secure_ram is used to track the location. In systems
the RAM base is not zero, or RAM is divided into banks,
this variable needs to be recalcuated to get the address.
- CONFIG_SYS_SDRAM_BASE:
Physical start address of SDRAM. _Must_ be 0 here.
- CONFIG_SYS_FLASH_BASE:
Physical start address of Flash memory.
- CONFIG_SYS_MALLOC_LEN:
Size of DRAM reserved for malloc() use.
- CONFIG_SYS_MALLOC_F_LEN
Size of the malloc() pool for use before relocation. If
this is defined, then a very simple malloc() implementation
will become available before relocation. The address is just
below the global data, and the stack is moved down to make
space.
This feature allocates regions with increasing addresses
within the region. calloc() is supported, but realloc()
is not available. free() is supported but does nothing.
The memory will be freed (or in fact just forgotten) when
U-Boot relocates itself.
- CONFIG_SYS_MALLOC_SIMPLE
Provides a simple and small malloc() and calloc() for those
boards which do not use the full malloc in SPL (which is
enabled with CONFIG_SYS_SPL_MALLOC).
- CONFIG_SYS_NONCACHED_MEMORY:
Size of non-cached memory area. This area of memory will be
typically located right below the malloc() area and mapped
uncached in the MMU. This is useful for drivers that would
otherwise require a lot of explicit cache maintenance. For
some drivers it's also impossible to properly maintain the
cache. For example if the regions that need to be flushed
are not a multiple of the cache-line size, *and* padding
cannot be allocated between the regions to align them (i.e.
if the HW requires a contiguous array of regions, and the
size of each region is not cache-aligned), then a flush of
one region may result in overwriting data that hardware has
written to another region in the same cache-line. This can
happen for example in network drivers where descriptors for
buffers are typically smaller than the CPU cache-line (e.g.
16 bytes vs. 32 or 64 bytes).
Non-cached memory is only supported on 32-bit ARM at present.
- CONFIG_SYS_BOOTMAPSZ:
Maximum size of memory mapped by the startup code of
the Linux kernel; all data that must be processed by
the Linux kernel (bd_info, boot arguments, FDT blob if
used) must be put below this limit, unless "bootm_low"
environment variable is defined and non-zero. In such case
all data for the Linux kernel must be between "bootm_low"
and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
variable "bootm_mapsize" will override the value of
CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
then the value in "bootm_size" will be used instead.
- CONFIG_SYS_BOOT_GET_CMDLINE:
Enables allocating and saving kernel cmdline in space between
"bootm_low" and "bootm_low" + BOOTMAPSZ.
- CONFIG_SYS_BOOT_GET_KBD:
Enables allocating and saving a kernel copy of the bd_info in
space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
- CONFIG_SYS_FLASH_PROTECTION
If defined, hardware flash sectors protection is used
instead of U-Boot software protection.
- CONFIG_SYS_FLASH_CFI:
Define if the flash driver uses extra elements in the
common flash structure for storing flash geometry.
- CONFIG_FLASH_CFI_DRIVER
This option also enables the building of the cfi_flash driver
in the drivers directory
- CONFIG_FLASH_CFI_MTD
This option enables the building of the cfi_mtd driver
in the drivers directory. The driver exports CFI flash
to the MTD layer.
- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
Use buffered writes to flash.
- CONFIG_FLASH_SPANSION_S29WS_N
s29ws-n MirrorBit flash has non-standard addresses for buffered
write commands.
- CONFIG_FLASH_SHOW_PROGRESS
If defined (must be an integer), print out countdown
digits and dots. Recommended value: 45 (9..1) for 80
column displays, 15 (3..1) for 40 column displays.
- CONFIG_FLASH_VERIFY
If defined, the content of the flash (destination) is compared
against the source after the write operation. An error message
will be printed when the contents are not identical.
Please note that this option is useless in nearly all cases,
since such flash programming errors usually are detected earlier
while unprotecting/erasing/programming. Please only enable
this option if you really know what you are doing.
- CONFIG_ENV_FLAGS_LIST_DEFAULT
- CONFIG_ENV_FLAGS_LIST_STATIC
Enable validation of the values given to environment variables when
calling env set. Variables can be restricted to only decimal,
hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
the variables can also be restricted to IP address or MAC address.
The format of the list is:
type_attribute = [s|d|x|b|i|m]
access_attribute = [a|r|o|c]
attributes = type_attribute[access_attribute]
entry = variable_name[:attributes]
list = entry[,list]
The type attributes are:
s - String (default)
d - Decimal
x - Hexadecimal
b - Boolean ([1yYtT|0nNfF])
i - IP address
m - MAC address
The access attributes are:
a - Any (default)
r - Read-only
o - Write-once
c - Change-default
- CONFIG_ENV_FLAGS_LIST_DEFAULT
Define this to a list (string) to define the ".flags"
environment variable in the default or embedded environment.
- CONFIG_ENV_FLAGS_LIST_STATIC
Define this to a list (string) to define validation that
should be done if an entry is not found in the ".flags"
environment variable. To override a setting in the static
list, simply add an entry for the same variable name to the
".flags" variable.
If CONFIG_REGEX is defined, the variable_name above is evaluated as a
regular expression. This allows multiple variables to define the same
flags without explicitly listing them for each variable.
The following definitions that deal with the placement and management
of environment data (variable area); in general, we support the
following configurations:
- CONFIG_BUILD_ENVCRC:
Builds up envcrc with the target environment so that external utils
may easily extract it and embed it in final U-Boot images.
BE CAREFUL! The first access to the environment happens quite early
in U-Boot initialization (when we try to get the setting of for the
console baudrate). You *MUST* have mapped your NVRAM area then, or
U-Boot will hang.
Please note that even with NVRAM we still use a copy of the
environment in RAM: we could work on NVRAM directly, but we want to
keep settings there always unmodified except somebody uses "saveenv"
to save the current settings.
BE CAREFUL! For some special cases, the local device can not use
"saveenv" command. For example, the local device will get the
environment stored in a remote NOR flash by SRIO or PCIE link,
but it can not erase, write this NOR flash by SRIO or PCIE interface.
- CONFIG_NAND_ENV_DST
Defines address in RAM to which the nand_spl code should copy the
environment. If redundant environment is used, it will be copied to
CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
Please note that the environment is read-only until the monitor
has been relocated to RAM and a RAM copy of the environment has been
created; also, when using EEPROM you will have to use env_get_f()
until then to read environment variables.
The environment is protected by a CRC32 checksum. Before the monitor
is relocated into RAM, as a result of a bad CRC you will be working
with the compiled-in default environment - *silently*!!! [This is
necessary, because the first environment variable we need is the
"baudrate" setting for the console - if we have a bad CRC, we don't
have any device yet where we could complain.]
Note: once the monitor has been relocated, then it will complain if
the default environment is used; a new CRC is computed as soon as you
use the "saveenv" command to store a valid environment.
- CONFIG_SYS_FAULT_MII_ADDR:
MII address of the PHY to check for the Ethernet link state.
- CONFIG_NS16550_MIN_FUNCTIONS:
Define this if you desire to only have use of the NS16550_init
and NS16550_putc functions for the serial driver located at
drivers/serial/ns16550.c. This option is useful for saving
space for already greatly restricted images, including but not
limited to NAND_SPL configurations.
- CONFIG_DISPLAY_BOARDINFO
Display information about the board that U-Boot is running on
when U-Boot starts up. The board function checkboard() is called
to do this.
- CONFIG_DISPLAY_BOARDINFO_LATE
Similar to the previous option, but display this information
later, once stdio is running and output goes to the LCD, if
present.
Low Level (hardware related) configuration options:
---------------------------------------------------
- CONFIG_SYS_CACHELINE_SIZE:
Cache Line Size of the CPU.
- CONFIG_SYS_CCSRBAR_DEFAULT:
Default (power-on reset) physical address of CCSR on Freescale
PowerPC SOCs.
- CONFIG_SYS_CCSRBAR:
Virtual address of CCSR. On a 32-bit build, this is typically
the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
- CONFIG_SYS_CCSRBAR_PHYS:
Physical address of CCSR. CCSR can be relocated to a new
physical address, if desired. In this case, this macro should
be set to that address. Otherwise, it should be set to the
same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
is typically relocated on 36-bit builds. It is recommended
that this macro be defined via the _HIGH and _LOW macros:
#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
either 0 (32-bit build) or 0xF (36-bit build). This macro is
used in assembly code, so it must not contain typecasts or
integer size suffixes (e.g. "ULL").
- CONFIG_SYS_CCSRBAR_PHYS_LOW:
Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
used in assembly code, so it must not contain typecasts or
integer size suffixes (e.g. "ULL").
- CONFIG_SYS_IMMR: Physical address of the Internal Memory.
DO NOT CHANGE unless you know exactly what you're
doing! (11-4) [MPC8xx systems only]
- CONFIG_SYS_INIT_RAM_ADDR:
Start address of memory area that can be used for
initial data and stack; please note that this must be
writable memory that is working WITHOUT special
initialization, i. e. you CANNOT use normal RAM which
will become available only after programming the
memory controller and running certain initialization
sequences.
U-Boot uses the following memory types:
- MPC8xx: IMMR (internal memory of the CPU)
- CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
- CONFIG_SYS_OR_TIMING_SDRAM:
SDRAM timing
- CONFIG_SYS_SRIO:
Chip has SRIO or not
- CONFIG_SRIO1:
Board has SRIO 1 port available
- CONFIG_SRIO2:
Board has SRIO 2 port available
- CONFIG_SRIO_PCIE_BOOT_MASTER
Board can support master function for Boot from SRIO and PCIE
- CONFIG_SYS_SRIOn_MEM_VIRT:
Virtual Address of SRIO port 'n' memory region
- CONFIG_SYS_SRIOn_MEM_PHYxS:
Physical Address of SRIO port 'n' memory region
- CONFIG_SYS_SRIOn_MEM_SIZE:
Size of SRIO port 'n' memory region
- CONFIG_SYS_NAND_BUSWIDTH_16BIT
Defined to tell the NAND controller that the NAND chip is using
a 16 bit bus.
Not all NAND drivers use this symbol.
Example of drivers that use it:
- drivers/mtd/nand/raw/ndfc.c
- drivers/mtd/nand/raw/mxc_nand.c
- CONFIG_SYS_NDFC_EBC0_CFG
Sets the EBC0_CFG register for the NDFC. If not defined
a default value will be used.
- CONFIG_SPD_EEPROM
Get DDR timing information from an I2C EEPROM. Common
with pluggable memory modules such as SODIMMs
SPD_EEPROM_ADDRESS
I2C address of the SPD EEPROM
- CONFIG_SYS_SPD_BUS_NUM
If SPD EEPROM is on an I2C bus other than the first
one, specify here. Note that the value must resolve
to something your driver can deal with.
- CONFIG_FSL_DDR_INTERACTIVE
Enable interactive DDR debugging. See doc/README.fsl-ddr.
- CONFIG_FSL_DDR_SYNC_REFRESH
Enable sync of refresh for multiple controllers.
- CONFIG_FSL_DDR_BIST
Enable built-in memory test for Freescale DDR controllers.
- CONFIG_RMII
Enable RMII mode for all FECs.
Note that this is a global option, we can't
have one FEC in standard MII mode and another in RMII mode.
- CONFIG_CRC32_VERIFY
Add a verify option to the crc32 command.
The syntax is:
=> crc32 -v <address> <count> <crc32>
Where address/count indicate a memory area
and crc32 is the correct crc32 which the
area should have.
- CONFIG_LOOPW
Add the "loopw" memory command. This only takes effect if
the memory commands are activated globally (CONFIG_CMD_MEMORY).
- CONFIG_CMD_MX_CYCLIC
Add the "mdc" and "mwc" memory commands. These are cyclic
"md/mw" commands.
Examples:
=> mdc.b 10 4 500
This command will print 4 bytes (10,11,12,13) each 500 ms.
=> mwc.l 100 12345678 10
This command will write 12345678 to address 100 all 10 ms.
This only takes effect if the memory commands are activated
globally (CONFIG_CMD_MEMORY).
- CONFIG_SPL_BUILD
Set when the currently-running compilation is for an artifact
that will end up in the SPL (as opposed to the TPL or U-Boot
proper). Code that needs stage-specific behavior should check
this.
- CONFIG_TPL_BUILD
Set when the currently-running compilation is for an artifact
that will end up in the TPL (as opposed to the SPL or U-Boot
proper). Code that needs stage-specific behavior should check
this.
- CONFIG_ARCH_MAP_SYSMEM
Generally U-Boot (and in particular the md command) uses
effective address. It is therefore not necessary to regard
U-Boot address as virtual addresses that need to be translated
to physical addresses. However, sandbox requires this, since
it maintains its own little RAM buffer which contains all
addressable memory. This option causes some memory accesses
to be mapped through map_sysmem() / unmap_sysmem().
- CONFIG_X86_RESET_VECTOR
If defined, the x86 reset vector code is included. This is not
needed when U-Boot is running from Coreboot.
- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
Option to disable subpage write in NAND driver
driver that uses this:
drivers/mtd/nand/raw/davinci_nand.c
Freescale QE/FMAN Firmware Support:
-----------------------------------
The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
loading of "firmware", which is encoded in the QE firmware binary format.
This firmware often needs to be loaded during U-Boot booting, so macros
are used to identify the storage device (NOR flash, SPI, etc) and the address
within that device.
- CONFIG_SYS_FMAN_FW_ADDR
The address in the storage device where the FMAN microcode is located. The
meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
is also specified.
- CONFIG_SYS_QE_FW_ADDR
The address in the storage device where the QE microcode is located. The
meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
is also specified.
- CONFIG_SYS_QE_FMAN_FW_LENGTH
The maximum possible size of the firmware. The firmware binary format
has a field that specifies the actual size of the firmware, but it
might not be possible to read any part of the firmware unless some
local storage is allocated to hold the entire firmware first.
- CONFIG_SYS_QE_FMAN_FW_IN_NOR
Specifies that QE/FMAN firmware is located in NOR flash, mapped as
normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
virtual address in NOR flash.
- CONFIG_SYS_QE_FMAN_FW_IN_NAND
Specifies that QE/FMAN firmware is located in NAND flash.
CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
- CONFIG_SYS_QE_FMAN_FW_IN_MMC
Specifies that QE/FMAN firmware is located on the primary SD/MMC
device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
Specifies that QE/FMAN firmware is located in the remote (master)
memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
window->master inbound window->master LAW->the ucode address in
master's memory space.
Freescale Layerscape Management Complex Firmware Support:
---------------------------------------------------------
The Freescale Layerscape Management Complex (MC) supports the loading of
"firmware".
This firmware often needs to be loaded during U-Boot booting, so macros
are used to identify the storage device (NOR flash, SPI, etc) and the address
within that device.
- CONFIG_FSL_MC_ENET
Enable the MC driver for Layerscape SoCs.
Freescale Layerscape Debug Server Support:
-------------------------------------------
The Freescale Layerscape Debug Server Support supports the loading of
"Debug Server firmware" and triggering SP boot-rom.
This firmware often needs to be loaded during U-Boot booting.
- CONFIG_SYS_MC_RSV_MEM_ALIGN
Define alignment of reserved memory MC requires
Reproducible builds
-------------------
In order to achieve reproducible builds, timestamps used in the U-Boot build
process have to be set to a fixed value.
This is done using the SOURCE_DATE_EPOCH environment variable.
SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
option for U-Boot or an environment variable in U-Boot.
SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
Building the Software:
======================
Building U-Boot has been tested in several native build environments
and in many different cross environments. Of course we cannot support
all possibly existing versions of cross development tools in all
(potentially obsolete) versions. In case of tool chain problems we
recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
which is extensively used to build and test U-Boot.
If you are not using a native environment, it is assumed that you
have GNU cross compiling tools available in your path. In this case,
you must set the environment variable CROSS_COMPILE in your shell.
Note that no changes to the Makefile or any other source files are
necessary. For example using the ELDK on a 4xx CPU, please enter:
$ CROSS_COMPILE=ppc_4xx-
$ export CROSS_COMPILE
U-Boot is intended to be simple to build. After installing the
sources you must configure U-Boot for one specific board type. This
is done by typing:
make NAME_defconfig
where "NAME_defconfig" is the name of one of the existing configu-
rations; see configs/*_defconfig for supported names.
Note: for some boards special configuration names may exist; check if
additional information is available from the board vendor; for
instance, the TQM823L systems are available without (standard)
or with LCD support. You can select such additional "features"
when choosing the configuration, i. e.
make TQM823L_defconfig
- will configure for a plain TQM823L, i. e. no LCD support
make TQM823L_LCD_defconfig
- will configure for a TQM823L with U-Boot console on LCD
etc.
Finally, type "make all", and you should get some working U-Boot
images ready for download to / installation on your system:
- "u-boot.bin" is a raw binary image
- "u-boot" is an image in ELF binary format
- "u-boot.srec" is in Motorola S-Record format
By default the build is performed locally and the objects are saved
in the source directory. One of the two methods can be used to change
this behavior and build U-Boot to some external directory:
1. Add O= to the make command line invocations:
make O=/tmp/build distclean
make O=/tmp/build NAME_defconfig
make O=/tmp/build all
2. Set environment variable KBUILD_OUTPUT to point to the desired location:
export KBUILD_OUTPUT=/tmp/build
make distclean
make NAME_defconfig
make all
Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
variable.
User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
For example to treat all compiler warnings as errors:
make KCFLAGS=-Werror
Please be aware that the Makefiles assume you are using GNU make, so
for instance on NetBSD you might need to use "gmake" instead of
native "make".
If the system board that you have is not listed, then you will need
to port U-Boot to your hardware platform. To do this, follow these
steps:
1. Create a new directory to hold your board specific code. Add any
files you need. In your board directory, you will need at least
the "Makefile" and a "<board>.c".
2. Create a new configuration file "include/configs/<board>.h" for
your board.
3. If you're porting U-Boot to a new CPU, then also create a new
directory to hold your CPU specific code. Add any files you need.
4. Run "make <board>_defconfig" with your new name.
5. Type "make", and you should get a working "u-boot.srec" file
to be installed on your target system.
6. Debug and solve any problems that might arise.
[Of course, this last step is much harder than it sounds.]
Testing of U-Boot Modifications, Ports to New Hardware, etc.:
==============================================================
If you have modified U-Boot sources (for instance added a new board
or support for new devices, a new CPU, etc.) you are expected to
provide feedback to the other developers. The feedback normally takes
the form of a "patch", i.e. a context diff against a certain (latest
official or latest in the git repository) version of U-Boot sources.
But before you submit such a patch, please verify that your modifi-
cation did not break existing code. At least make sure that *ALL* of
the supported boards compile WITHOUT ANY compiler warnings. To do so,
just run the buildman script (tools/buildman/buildman), which will
configure and build U-Boot for ALL supported system. Be warned, this
will take a while. Please see the buildman README, or run 'buildman -H'
for documentation.
See also "U-Boot Porting Guide" below.
Monitor Commands - Overview:
============================
go - start application at address 'addr'
run - run commands in an environment variable
bootm - boot application image from memory
bootp - boot image via network using BootP/TFTP protocol
bootz - boot zImage from memory
tftpboot- boot image via network using TFTP protocol
and env variables "ipaddr" and "serverip"
(and eventually "gatewayip")
tftpput - upload a file via network using TFTP protocol
rarpboot- boot image via network using RARP/TFTP protocol
diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
loads - load S-Record file over serial line
loadb - load binary file over serial line (kermit mode)
loadm - load binary blob from source address to destination address
md - memory display
mm - memory modify (auto-incrementing)
nm - memory modify (constant address)
mw - memory write (fill)
ms - memory search
cp - memory copy
cmp - memory compare
crc32 - checksum calculation
i2c - I2C sub-system
sspi - SPI utility commands
base - print or set address offset
printenv- print environment variables
pwm - control pwm channels
setenv - set environment variables
saveenv - save environment variables to persistent storage
protect - enable or disable FLASH write protection
erase - erase FLASH memory
flinfo - print FLASH memory information
nand - NAND memory operations (see doc/README.nand)
bdinfo - print Board Info structure
iminfo - print header information for application image
coninfo - print console devices and informations
ide - IDE sub-system
loop - infinite loop on address range
loopw - infinite write loop on address range
mtest - simple RAM test
icache - enable or disable instruction cache
dcache - enable or disable data cache
reset - Perform RESET of the CPU
echo - echo args to console
version - print monitor version
help - print online help
? - alias for 'help'
Monitor Commands - Detailed Description:
========================================
TODO.
For now: just type "help <command>".
Note for Redundant Ethernet Interfaces:
=======================================
Some boards come with redundant Ethernet interfaces; U-Boot supports
such configurations and is capable of automatic selection of a
"working" interface when needed. MAC assignment works as follows:
Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
"eth1addr" (=>eth1), "eth2addr", ...
If the network interface stores some valid MAC address (for instance
in SROM), this is used as default address if there is NO correspon-
ding setting in the environment; if the corresponding environment
variable is set, this overrides the settings in the card; that means:
o If the SROM has a valid MAC address, and there is no address in the
environment, the SROM's address is used.
o If there is no valid address in the SROM, and a definition in the
environment exists, then the value from the environment variable is
used.
o If both the SROM and the environment contain a MAC address, and
both addresses are the same, this MAC address is used.
o If both the SROM and the environment contain a MAC address, and the
addresses differ, the value from the environment is used and a
warning is printed.
o If neither SROM nor the environment contain a MAC address, an error
is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
a random, locally-assigned MAC is used.
If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
will be programmed into hardware as part of the initialization process. This
may be skipped by setting the appropriate 'ethmacskip' environment variable.
The naming convention is as follows:
"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
Image Formats:
==============
U-Boot is capable of booting (and performing other auxiliary operations on)
images in two formats:
New uImage format (FIT)
-----------------------
Flexible and powerful format based on Flattened Image Tree -- FIT (similar
to Flattened Device Tree). It allows the use of images with multiple
components (several kernels, ramdisks, etc.), with contents protected by
SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
Old uImage format
-----------------
Old image format is based on binary files which can be basically anything,
preceded by a special header; see the definitions in include/image.h for
details; basically, the header defines the following image properties:
* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
* Compression Type (uncompressed, gzip, bzip2)
* Load Address
* Entry Point
* Image Name
* Image Timestamp
The header is marked by a special Magic Number, and both the header
and the data portions of the image are secured against corruption by
CRC32 checksums.
Linux Support:
==============
Although U-Boot should support any OS or standalone application
easily, the main focus has always been on Linux during the design of
U-Boot.
U-Boot includes many features that so far have been part of some
special "boot loader" code within the Linux kernel. Also, any
"initrd" images to be used are no longer part of one big Linux image;
instead, kernel and "initrd" are separate images. This implementation
serves several purposes:
- the same features can be used for other OS or standalone
applications (for instance: using compressed images to reduce the
Flash memory footprint)
- it becomes much easier to port new Linux kernel versions because
lots of low-level, hardware dependent stuff are done by U-Boot
- the same Linux kernel image can now be used with different "initrd"
images; of course this also means that different kernel images can
be run with the same "initrd". This makes testing easier (you don't
have to build a new "zImage.initrd" Linux image when you just
change a file in your "initrd"). Also, a field-upgrade of the
software is easier now.
Linux HOWTO:
============
Porting Linux to U-Boot based systems:
---------------------------------------
U-Boot cannot save you from doing all the necessary modifications to
configure the Linux device drivers for use with your target hardware
(no, we don't intend to provide a full virtual machine interface to
Linux :-).
But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
Just make sure your machine specific header file (for instance
include/asm-ppc/tqm8xx.h) includes the same definition of the Board
Information structure as we define in include/asm-<arch>/u-boot.h,
and make sure that your definition of IMAP_ADDR uses the same value
as your U-Boot configuration in CONFIG_SYS_IMMR.
Note that U-Boot now has a driver model, a unified model for drivers.
If you are adding a new driver, plumb it into driver model. If there
is no uclass available, you are encouraged to create one. See
doc/driver-model.
Configuring the Linux kernel:
-----------------------------
No specific requirements for U-Boot. Make sure you have some root
device (initial ramdisk, NFS) for your target system.
Building a Linux Image:
-----------------------
With U-Boot, "normal" build targets like "zImage" or "bzImage" are
not used. If you use recent kernel source, a new build target
"uImage" will exist which automatically builds an image usable by
U-Boot. Most older kernels also have support for a "pImage" target,
which was introduced for our predecessor project PPCBoot and uses a
100% compatible format.
Example:
make TQM850L_defconfig
make oldconfig
make dep
make uImage
The "uImage" build target uses a special tool (in 'tools/mkimage') to
encapsulate a compressed Linux kernel image with header information,
CRC32 checksum etc. for use with U-Boot. This is what we are doing:
* build a standard "vmlinux" kernel image (in ELF binary format):
* convert the kernel into a raw binary image:
${CROSS_COMPILE}-objcopy -O binary \
-R .note -R .comment \
-S vmlinux linux.bin
* compress the binary image:
gzip -9 linux.bin
* package compressed binary image for U-Boot:
mkimage -A ppc -O linux -T kernel -C gzip \
-a 0 -e 0 -n "Linux Kernel Image" \
-d linux.bin.gz uImage
The "mkimage" tool can also be used to create ramdisk images for use
with U-Boot, either separated from the Linux kernel image, or
combined into one file. "mkimage" encapsulates the images with a 64
byte header containing information about target architecture,
operating system, image type, compression method, entry points, time
stamp, CRC32 checksums, etc.
"mkimage" can be called in two ways: to verify existing images and
print the header information, or to build new images.
In the first form (with "-l" option) mkimage lists the information
contained in the header of an existing U-Boot image; this includes
checksum verification:
tools/mkimage -l image
-l ==> list image header information
The second form (with "-d" option) is used to build a U-Boot image
from a "data file" which is used as image payload:
tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
-n name -d data_file image
-A ==> set architecture to 'arch'
-O ==> set operating system to 'os'
-T ==> set image type to 'type'
-C ==> set compression type 'comp'
-a ==> set load address to 'addr' (hex)
-e ==> set entry point to 'ep' (hex)
-n ==> set image name to 'name'
-d ==> use image data from 'datafile'
Right now, all Linux kernels for PowerPC systems use the same load
address (0x00000000), but the entry point address depends on the
kernel version:
- 2.2.x kernels have the entry point at 0x0000000C,
- 2.3.x and later kernels have the entry point at 0x00000000.
So a typical call to build a U-Boot image would read:
-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
> examples/uImage.TQM850L
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point: 0x00000000
To verify the contents of the image (or check for corruption):
-> tools/mkimage -l examples/uImage.TQM850L
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point: 0x00000000
NOTE: for embedded systems where boot time is critical you can trade
speed for memory and install an UNCOMPRESSED image instead: this
needs more space in Flash, but boots much faster since it does not
need to be uncompressed:
-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
> examples/uImage.TQM850L-uncompressed
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (uncompressed)
Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
Load Address: 0x00000000
Entry Point: 0x00000000
Similar you can build U-Boot images from a 'ramdisk.image.gz' file
when your kernel is intended to use an initial ramdisk:
-> tools/mkimage -n 'Simple Ramdisk Image' \
> -A ppc -O linux -T ramdisk -C gzip \
> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
Image Name: Simple Ramdisk Image
Created: Wed Jan 12 14:01:50 2000
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
Load Address: 0x00000000
Entry Point: 0x00000000
The "dumpimage" tool can be used to disassemble or list the contents of images
built by mkimage. See dumpimage's help output (-h) for details.
Installing a Linux Image:
-------------------------
To downloading a U-Boot image over the serial (console) interface,
you must convert the image to S-Record format:
objcopy -I binary -O srec examples/image examples/image.srec
The 'objcopy' does not understand the information in the U-Boot
image header, so the resulting S-Record file will be relative to
address 0x00000000. To load it to a given address, you need to
specify the target address as 'offset' parameter with the 'loads'
command.
Example: install the image to address 0x40100000 (which on the
TQM8xxL is in the first Flash bank):
=> erase 40100000 401FFFFF
.......... done
Erased 8 sectors
=> loads 40100000
## Ready for S-Record download ...
~>examples/image.srec
1 2 3 4 5 6 7 8 9 10 11 12 13 ...
...
15989 15990 15991 15992
[file transfer complete]
[connected]
## Start Addr = 0x00000000
You can check the success of the download using the 'iminfo' command;
this includes a checksum verification so you can be sure no data
corruption happened:
=> imi 40100000
## Checking Image at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Boot Linux:
-----------
The "bootm" command is used to boot an application that is stored in
memory (RAM or Flash). In case of a Linux kernel image, the contents
of the "bootargs" environment variable is passed to the kernel as
parameters. You can check and modify this variable using the
"printenv" and "setenv" commands:
=> printenv bootargs
bootargs=root=/dev/ram
=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
=> printenv bootargs
bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
=> bootm 40020000
## Booting Linux kernel at 40020000 ...
Image Name: 2.2.13 for NFS on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 381681 Bytes = 372 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
...
If you want to boot a Linux kernel with initial RAM disk, you pass
the memory addresses of both the kernel and the initrd image (PPBCOOT
format!) to the "bootm" command:
=> imi 40100000 40200000
## Checking Image at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
## Checking Image at 40200000 ...
Image Name: Simple Ramdisk Image
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
=> bootm 40100000 40200000
## Booting Linux kernel at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
## Loading RAMDisk Image at 40200000 ...
Image Name: Simple Ramdisk Image
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Loading Ramdisk ... OK
Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
Boot arguments: root=/dev/ram
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
...
RAMDISK: Compressed image found at block 0
VFS: Mounted root (ext2 filesystem).
bash#
Boot Linux and pass a flat device tree:
-----------
First, U-Boot must be compiled with the appropriate defines. See the section
titled "Linux Kernel Interface" above for a more in depth explanation. The
following is an example of how to start a kernel and pass an updated
flat device tree:
=> print oftaddr
oftaddr=0x300000
=> print oft
oft=oftrees/mpc8540ads.dtb
=> tftp $oftaddr $oft
Speed: 1000, full duplex
Using TSEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.1.101
Filename 'oftrees/mpc8540ads.dtb'.
Load address: 0x300000
Loading: #
done
Bytes transferred = 4106 (100a hex)
=> tftp $loadaddr $bootfile
Speed: 1000, full duplex
Using TSEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.1.2
Filename 'uImage'.
Load address: 0x200000
Loading:############
done
Bytes transferred = 1029407 (fb51f hex)
=> print loadaddr
loadaddr=200000
=> print oftaddr
oftaddr=0x300000
=> bootm $loadaddr - $oftaddr
## Booting image at 00200000 ...
Image Name: Linux-2.6.17-dirty
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 1029343 Bytes = 1005.2 kB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Booting using flat device tree at 0x300000
Using MPC85xx ADS machine description
Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
[snip]
More About U-Boot Image Types:
------------------------------
U-Boot supports the following image types:
"Standalone Programs" are directly runnable in the environment
provided by U-Boot; it is expected that (if they behave
well) you can continue to work in U-Boot after return from
the Standalone Program.
"OS Kernel Images" are usually images of some Embedded OS which
will take over control completely. Usually these programs
will install their own set of exception handlers, device
drivers, set up the MMU, etc. - this means, that you cannot
expect to re-enter U-Boot except by resetting the CPU.
"RAMDisk Images" are more or less just data blocks, and their
parameters (address, size) are passed to an OS kernel that is
being started.
"Multi-File Images" contain several images, typically an OS
(Linux) kernel image and one or more data images like
RAMDisks. This construct is useful for instance when you want
to boot over the network using BOOTP etc., where the boot
server provides just a single image file, but you want to get
for instance an OS kernel and a RAMDisk image.
"Multi-File Images" start with a list of image sizes, each
image size (in bytes) specified by an "uint32_t" in network
byte order. This list is terminated by an "(uint32_t)0".
Immediately after the terminating 0 follow the images, one by
one, all aligned on "uint32_t" boundaries (size rounded up to
a multiple of 4 bytes).
"Firmware Images" are binary images containing firmware (like
U-Boot or FPGA images) which usually will be programmed to
flash memory.
"Script files" are command sequences that will be executed by
U-Boot's command interpreter; this feature is especially
useful when you configure U-Boot to use a real shell (hush)
as command interpreter.
Booting the Linux zImage:
-------------------------
On some platforms, it's possible to boot Linux zImage. This is done
using the "bootz" command. The syntax of "bootz" command is the same
as the syntax of "bootm" command.
Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
kernel with raw initrd images. The syntax is slightly different, the
address of the initrd must be augmented by it's size, in the following
format: "<initrd addres>:<initrd size>".
Standalone HOWTO:
=================
One of the features of U-Boot is that you can dynamically load and
run "standalone" applications, which can use some resources of
U-Boot like console I/O functions or interrupt services.
Two simple examples are included with the sources:
"Hello World" Demo:
-------------------
'examples/hello_world.c' contains a small "Hello World" Demo
application; it is automatically compiled when you build U-Boot.
It's configured to run at address 0x00040004, so you can play with it
like that:
=> loads
## Ready for S-Record download ...
~>examples/hello_world.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004
=> go 40004 Hello World! This is a test.
## Starting application at 0x00040004 ...
Hello World
argc = 7
argv[0] = "40004"
argv[1] = "Hello"
argv[2] = "World!"
argv[3] = "This"
argv[4] = "is"
argv[5] = "a"
argv[6] = "test."
argv[7] = "<NULL>"
Hit any key to exit ...
## Application terminated, rc = 0x0
Another example, which demonstrates how to register a CPM interrupt
handler with the U-Boot code, can be found in 'examples/timer.c'.
Here, a CPM timer is set up to generate an interrupt every second.
The interrupt service routine is trivial, just printing a '.'
character, but this is just a demo program. The application can be
controlled by the following keys:
? - print current values og the CPM Timer registers
b - enable interrupts and start timer
e - stop timer and disable interrupts
q - quit application
=> loads
## Ready for S-Record download ...
~>examples/timer.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004
=> go 40004
## Starting application at 0x00040004 ...
TIMERS=0xfff00980
Using timer 1
tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
Hit 'b':
[q, b, e, ?] Set interval 1000000 us
Enabling timer
Hit '?':
[q, b, e, ?] ........
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
Hit 'e':
[q, b, e, ?] ...Stopping timer
Hit 'q':
[q, b, e, ?] ## Application terminated, rc = 0x0
Minicom warning:
================
Over time, many people have reported problems when trying to use the
"minicom" terminal emulation program for serial download. I (wd)
consider minicom to be broken, and recommend not to use it. Under
Unix, I recommend to use C-Kermit for general purpose use (and
especially for kermit binary protocol download ("loadb" command), and
use "cu" for S-Record download ("loads" command). See
https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
for help with kermit.
Nevertheless, if you absolutely want to use it try adding this
configuration to your "File transfer protocols" section:
Name Program Name U/D FullScr IO-Red. Multi
X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
NetBSD Notes:
=============
Starting at version 0.9.2, U-Boot supports NetBSD both as host
(build U-Boot) and target system (boots NetBSD/mpc8xx).
Building requires a cross environment; it is known to work on
NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
need gmake since the Makefiles are not compatible with BSD make).
Note that the cross-powerpc package does not install include files;
attempting to build U-Boot will fail because <machine/ansi.h> is
missing. This file has to be installed and patched manually:
# cd /usr/pkg/cross/powerpc-netbsd/include
# mkdir powerpc
# ln -s powerpc machine
# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
# ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
Native builds *don't* work due to incompatibilities between native
and U-Boot include files.
Booting assumes that (the first part of) the image booted is a
stage-2 loader which in turn loads and then invokes the kernel
proper. Loader sources will eventually appear in the NetBSD source
tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
Implementation Internals:
=========================
The following is not intended to be a complete description of every
implementation detail. However, it should help to understand the
inner workings of U-Boot and make it easier to port it to custom
hardware.
Initial Stack, Global Data:
---------------------------
The implementation of U-Boot is complicated by the fact that U-Boot
starts running out of ROM (flash memory), usually without access to
system RAM (because the memory controller is not initialized yet).
This means that we don't have writable Data or BSS segments, and BSS
is not initialized as zero. To be able to get a C environment working
at all, we have to allocate at least a minimal stack. Implementation
options for this are defined and restricted by the CPU used: Some CPU
models provide on-chip memory (like the IMMR area on MPC8xx and
MPC826x processors), on others (parts of) the data cache can be
locked as (mis-) used as memory, etc.
Chris Hallinan posted a good summary of these issues to the
U-Boot mailing list:
Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
From: "Chris Hallinan" <clh@net1plus.com>
Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
...
Correct me if I'm wrong, folks, but the way I understand it
is this: Using DCACHE as initial RAM for Stack, etc, does not
require any physical RAM backing up the cache. The cleverness
is that the cache is being used as a temporary supply of
necessary storage before the SDRAM controller is setup. It's
beyond the scope of this list to explain the details, but you
can see how this works by studying the cache architecture and
operation in the architecture and processor-specific manuals.
OCM is On Chip Memory, which I believe the 405GP has 4K. It
is another option for the system designer to use as an
initial stack/RAM area prior to SDRAM being available. Either
option should work for you. Using CS 4 should be fine if your
board designers haven't used it for something that would
cause you grief during the initial boot! It is frequently not
used.
CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
with your processor/board/system design. The default value
you will find in any recent u-boot distribution in
walnut.h should work for you. I'd set it to a value larger
than your SDRAM module. If you have a 64MB SDRAM module, set
it above 400_0000. Just make sure your board has no resources
that are supposed to respond to that address! That code in
start.S has been around a while and should work as is when
you get the config right.
-Chris Hallinan
DS4.COM, Inc.
It is essential to remember this, since it has some impact on the C
code for the initialization procedures:
* Initialized global data (data segment) is read-only. Do not attempt
to write it.
* Do not use any uninitialized global data (or implicitly initialized
as zero data - BSS segment) at all - this is undefined, initiali-
zation is performed later (when relocating to RAM).
* Stack space is very limited. Avoid big data buffers or things like
that.
Having only the stack as writable memory limits means we cannot use
normal global data to share information between the code. But it
turned out that the implementation of U-Boot can be greatly
simplified by making a global data structure (gd_t) available to all
functions. We could pass a pointer to this data as argument to _all_
functions, but this would bloat the code. Instead we use a feature of
the GCC compiler (Global Register Variables) to share the data: we
place a pointer (gd) to the global data into a register which we
reserve for this purpose.
When choosing a register for such a purpose we are restricted by the
relevant (E)ABI specifications for the current architecture, and by
GCC's implementation.
For PowerPC, the following registers have specific use:
R1: stack pointer
R2: reserved for system use
R3-R4: parameter passing and return values
R5-R10: parameter passing
R13: small data area pointer
R30: GOT pointer
R31: frame pointer
(U-Boot also uses R12 as internal GOT pointer. r12
is a volatile register so r12 needs to be reset when
going back and forth between asm and C)
==> U-Boot will use R2 to hold a pointer to the global data
Note: on PPC, we could use a static initializer (since the
address of the global data structure is known at compile time),
but it turned out that reserving a register results in somewhat
smaller code - although the code savings are not that big (on
average for all boards 752 bytes for the whole U-Boot image,
624 text + 127 data).
On ARM, the following registers are used:
R0: function argument word/integer result
R1-R3: function argument word
R9: platform specific
R10: stack limit (used only if stack checking is enabled)
R11: argument (frame) pointer
R12: temporary workspace
R13: stack pointer
R14: link register
R15: program counter
==> U-Boot will use R9 to hold a pointer to the global data
Note: on ARM, only R_ARM_RELATIVE relocations are supported.
On Nios II, the ABI is documented here:
https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
==> U-Boot will use gp to hold a pointer to the global data
Note: on Nios II, we give "-G0" option to gcc and don't use gp
to access small data sections, so gp is free.
On RISC-V, the following registers are used:
x0: hard-wired zero (zero)
x1: return address (ra)
x2: stack pointer (sp)
x3: global pointer (gp)
x4: thread pointer (tp)
x5: link register (t0)
x8: frame pointer (fp)
x10-x11: arguments/return values (a0-1)
x12-x17: arguments (a2-7)
x28-31: temporaries (t3-6)
pc: program counter (pc)
==> U-Boot will use gp to hold a pointer to the global data
Memory Management:
------------------
U-Boot runs in system state and uses physical addresses, i.e. the
MMU is not used either for address mapping nor for memory protection.
The available memory is mapped to fixed addresses using the memory
controller. In this process, a contiguous block is formed for each
memory type (Flash, SDRAM, SRAM), even when it consists of several
physical memory banks.
U-Boot is installed in the first 128 kB of the first Flash bank (on
TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
booting and sizing and initializing DRAM, the code relocates itself
to the upper end of DRAM. Immediately below the U-Boot code some
memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
configuration setting]. Below that, a structure with global Board
Info data is placed, followed by the stack (growing downward).
Additionally, some exception handler code is copied to the low 8 kB
of DRAM (0x00000000 ... 0x00001FFF).
So a typical memory configuration with 16 MB of DRAM could look like
this:
0x0000 0000 Exception Vector code
:
0x0000 1FFF
0x0000 2000 Free for Application Use
:
:
:
:
0x00FB FF20 Monitor Stack (Growing downward)
0x00FB FFAC Board Info Data and permanent copy of global data
0x00FC 0000 Malloc Arena
:
0x00FD FFFF
0x00FE 0000 RAM Copy of Monitor Code
... eventually: LCD or video framebuffer
... eventually: pRAM (Protected RAM - unchanged by reset)
0x00FF FFFF [End of RAM]
System Initialization:
----------------------
In the reset configuration, U-Boot starts at the reset entry point
(on most PowerPC systems at address 0x00000100). Because of the reset
configuration for CS0# this is a mirror of the on board Flash memory.
To be able to re-map memory U-Boot then jumps to its link address.
To be able to implement the initialization code in C, a (small!)
initial stack is set up in the internal Dual Ported RAM (in case CPUs
which provide such a feature like), or in a locked part of the data
cache. After that, U-Boot initializes the CPU core, the caches and
the SIU.
Next, all (potentially) available memory banks are mapped using a
preliminary mapping. For example, we put them on 512 MB boundaries
(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
programmed for SDRAM access. Using the temporary configuration, a
simple memory test is run that determines the size of the SDRAM
banks.
When there is more than one SDRAM bank, and the banks are of
different size, the largest is mapped first. For equal size, the first
bank (CS2#) is mapped first. The first mapping is always for address
0x00000000, with any additional banks following immediately to create
contiguous memory starting from 0.
Then, the monitor installs itself at the upper end of the SDRAM area
and allocates memory for use by malloc() and for the global Board
Info data; also, the exception vector code is copied to the low RAM
pages, and the final stack is set up.
Only after this relocation will you have a "normal" C environment;
until that you are restricted in several ways, mostly because you are
running from ROM, and because the code will have to be relocated to a
new address in RAM.
U-Boot Porting Guide:
----------------------
[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
list, October 2002]
int main(int argc, char *argv[])
{
sighandler_t no_more_time;
signal(SIGALRM, no_more_time);
alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
if (available_money > available_manpower) {
Pay consultant to port U-Boot;
return 0;
}
Download latest U-Boot source;
Subscribe to u-boot mailing list;
if (clueless)
email("Hi, I am new to U-Boot, how do I get started?");
while (learning) {
Read the README file in the top level directory;
Read https://www.denx.de/wiki/bin/view/DULG/Manual;
Read applicable doc/README.*;
Read the source, Luke;
/* find . -name "*.[chS]" | xargs grep -i <keyword> */
}
if (available_money > toLocalCurrency ($2500))
Buy a BDI3000;
else
Add a lot of aggravation and time;
if (a similar board exists) { /* hopefully... */
cp -a board/<similar> board/<myboard>
cp include/configs/<similar>.h include/configs/<myboard>.h
} else {
Create your own board support subdirectory;
Create your own board include/configs/<myboard>.h file;
}
Edit new board/<myboard> files
Edit new include/configs/<myboard>.h
while (!accepted) {
while (!running) {
do {
Add / modify source code;
} until (compiles);
Debug;
if (clueless)
email("Hi, I am having problems...");
}
Send patch file to the U-Boot email list;
if (reasonable critiques)
Incorporate improvements from email list code review;
else
Defend code as written;
}
return 0;
}
void no_more_time (int sig)
{
hire_a_guru();
}
Coding Standards:
-----------------
All contributions to U-Boot should conform to the Linux kernel
coding style; see the kernel coding style guide at
https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
script "scripts/Lindent" in your Linux kernel source directory.
Source files originating from a different project (for example the
MTD subsystem) are generally exempt from these guidelines and are not
reformatted to ease subsequent migration to newer versions of those
sources.
Please note that U-Boot is implemented in C (and to some small parts in
Assembler); no C++ is used, so please do not use C++ style comments (//)
in your code.
Please also stick to the following formatting rules:
- remove any trailing white space
- use TAB characters for indentation and vertical alignment, not spaces
- make sure NOT to use DOS '\r\n' line feeds
- do not add more than 2 consecutive empty lines to source files
- do not add trailing empty lines to source files
Submissions which do not conform to the standards may be returned
with a request to reformat the changes.
Submitting Patches:
-------------------
Since the number of patches for U-Boot is growing, we need to
establish some rules. Submissions which do not conform to these rules
may be rejected, even when they contain important and valuable stuff.
Please see https://www.denx.de/wiki/U-Boot/Patches for details.
Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
see https://lists.denx.de/listinfo/u-boot
When you send a patch, please include the following information with
it:
* For bug fixes: a description of the bug and how your patch fixes
this bug. Please try to include a way of demonstrating that the
patch actually fixes something.
* For new features: a description of the feature and your
implementation.
* For major contributions, add a MAINTAINERS file with your
information and associated file and directory references.
* When you add support for a new board, don't forget to add a
maintainer e-mail address to the boards.cfg file, too.
* If your patch adds new configuration options, don't forget to
document these in the README file.
* The patch itself. If you are using git (which is *strongly*
recommended) you can easily generate the patch using the
"git format-patch". If you then use "git send-email" to send it to
the U-Boot mailing list, you will avoid most of the common problems
with some other mail clients.
If you cannot use git, use "diff -purN OLD NEW". If your version of
diff does not support these options, then get the latest version of
GNU diff.
The current directory when running this command shall be the parent
directory of the U-Boot source tree (i. e. please make sure that
your patch includes sufficient directory information for the
affected files).
We prefer patches as plain text. MIME attachments are discouraged,
and compressed attachments must not be used.
* If one logical set of modifications affects or creates several
files, all these changes shall be submitted in a SINGLE patch file.
* Changesets that contain different, unrelated modifications shall be
submitted as SEPARATE patches, one patch per changeset.
Notes:
* Before sending the patch, run the buildman script on your patched
source tree and make sure that no errors or warnings are reported
for any of the boards.
* Keep your modifications to the necessary minimum: A patch
containing several unrelated changes or arbitrary reformats will be
returned with a request to re-formatting / split it.
* If you modify existing code, make sure that your new code does not
add to the memory footprint of the code ;-) Small is beautiful!
When adding new features, these should compile conditionally only
(using #ifdef), and the resulting code with the new feature
disabled must not need more memory than the old code without your
modification.
* Remember that there is a size limit of 100 kB per message on the
u-boot mailing list. Bigger patches will be moderated. If they are
reasonable and not too big, they will be acknowledged. But patches
bigger than the size limit should be avoided.