# SPDX-License-Identifier: GPL-2.0+
#
# Copyright (C) 2015 Google. Inc
# Written by Simon Glass <sjg@chromium.org>

U-Boot on Rockchip
==================

A wide range of Rockchip SoCs are supported in mainline U-Boot


Prerequisites
=============

You will need:

   - Firefly RK3288 board or something else with a supported RockChip SoC
   - Power connection to 5V using the supplied micro-USB power cable
   - Separate USB serial cable attached to your computer and the Firefly
        (connect to the micro-USB connector below the logo)
   - rkflashtool [3]
   - openssl (sudo apt-get install openssl)
   - Serial UART connection [4]
   - Suitable ARM cross compiler, e.g.:
        sudo apt-get install gcc-4.7-arm-linux-gnueabi


Building
========

At present 11 RK3288 boards are supported:

   - EVB RK3288 - use evb-rk3288 configuration
   - Firefly RK3288 - use firefly-rk3288 configuration
   - Hisense Chromebook - use chromebook_jerry configuration
   - Asus C100P Chromebook - use chromebook_minnie configuration
   - Asus Chromebit - use chromebook_mickey configuration
   - MiQi RK3288 - use miqi-rk3288 configuration
   - phyCORE-RK3288 RDK - use phycore-rk3288 configuration
   - PopMetal RK3288 - use popmetal-rk3288 configuration
   - Radxa Rock 2 - use rock2 configuration
   - Tinker RK3288 - use tinker-rk3288 configuration
   - Vyasa RK3288 - use vyasa-rk3288 configuration

Two RK3036 boards are supported:

   - EVB RK3036 - use evb-rk3036 configuration
   - Kylin - use kylin_rk3036 configuration

Two RK3308 boards are supported:

   - EVB RK3308 - use evb-rk3308 configuration
   - ROC-CC-RK3308 - use roc-rk3308-cc configuration

Two RK3328 board are supported:

   - EVB RK3328 - use evb-rk3328_defconfig
   - Pine64 Rock64 board - use rock64-rk3328_defconfig

Size RK3399 boards are supported (aarch64):

   - EBV RK3399 - use evb_rk3399 configuration
   - Firefly RK3399 - use the firefly_rk3399 configuration
   - Puma - use puma_rk3399 configuration
   - Ficus - use ficus-rk3399 configuration
   - Rock960 (Vamrs) - use rock960-rk3399 configuration
   - Bob - use chromebook_bob configuration

Four RK3368 boards are supported:

   - Sheep - use sheep-rk3368 configuration
   - Lion - use lion-rk3368 configuration
   - Geekbox - use geekbox configuration
   - EVB PX5 - use evb-px5  configuration

One RK3128 board is supported:

   - EVB RK3128 - use evb-rk3128 configuration

One RK3229 board is supported:

   - EVB RK3229 - use evb-rk3229 configuration

Two RV1108 boards are supported:

   - EVB RV1108 - use evb-rv1108 configuration
   - Elgin R1 - use elgin-rv1108 configuration

One RV3188 baord is supported:

   - Raxda Rock - use rock configuration


For example:

1. To build RK3288 board:

   CROSS_COMPILE=arm-linux-gnueabi- make O=firefly firefly-rk3288_defconfig all

    (or you can use another cross compiler if you prefer)

2. To build RK3308 board:
   - Get the rkbin
     => git clone https://github.com/rockchip-linux/rkbin.git

   - Compile U-Boot
     => cd /path/to/u-boot
     => export BL31=/path/to/rkbin/bin/rk33/rk3308_bl31_v2.22.elf
     => make roc-rk3308-cc_defconfig
     => make CROSS_COMPILE=aarch64-linux-gnu- all
     => make CROSS_COMPILE=aarch64-linux-gnu- u-boot.itb
     => ./tools/mkimage -n rk3308 -T rksd -d /path/to/rkbin/bin/rk33/rk3308_ddr_589MHz_uart2_m0_v1.26.bin idbloader.img
     => cat spl/u-boot-spl.bin  >> idbloader.img

3. To build RK3399 board:

   Option 1: Package the image with Rockchip miniloader:

   - Compile U-Boot

     => cd /path/to/u-boot
     => make nanopi-neo4-rk3399_defconfig
     => make

   - Get the rkbin

     => git clone https://github.com/rockchip-linux/rkbin.git

   - Create trust.img

     => cd /path/to/rkbin
     => ./tools/trust_merger RKTRUST/RK3399TRUST.ini

   - Create uboot.img

     => cd /path/to/rkbin
     => ./tools/loaderimage --pack --uboot /path/to/u-boot/u-boot-dtb.bin uboot.img

     (Get trust.img and uboot.img)

   Option 2: Package the image with SPL:

   - Export cross compiler path for aarch64

   - Compile ATF

     For Puma board.

	=> git clone git://git.theobroma-systems.com/arm-trusted-firmware.git
	=> cd arm-trusted-firmware
	=> make CROSS_COMPILE=aarch64-linux-gnu- PLAT=rk3399 bl31

	(export bl31.bin)
	=> export BL31=/path/to/arm-trusted-firmware/build/rk3399/release/bl31/bl31.bin

     For rest of rk3399 boards.

	=> git clone https://github.com/ARM-software/arm-trusted-firmware.git
	=> cd arm-trusted-firmware

	(export cross compiler path for Cortex-M0 MCU likely arm-none-eabi-)
	=> make realclean
	=> make CROSS_COMPILE=aarch64-linux-gnu- PLAT=rk3399

	(export bl31.elf)
	=> export BL31=/path/to/arm-trusted-firmware/build/rk3399/release/bl31/bl31.elf

   - Compile PMU M0 firmware

     This is optional for most of the rk3399 boards and required only for Puma board.

     => git clone git://git.theobroma-systems.com/rk3399-cortex-m0.git
     => cd rk3399-cortex-m0

     (export cross compiler path for Cortex-M0 PMU)
     => make CROSS_COMPILE=arm-cortex_m0-eabi-

     (export rk3399m0.bin)
     => export PMUM0=/path/to/rk3399-cortex-m0/rk3399m0.bin

   - Compile U-Boot

     => cd /path/to/u-boot
     => make orangepi-rk3399_defconfig
     => make

     (Get spl/u-boot-spl-dtb.bin, u-boot.itb images and some boards would get
      spl/u-boot-spl.bin since it doesn't enable CONFIG_SPL_OF_CONTROL

      If TPL enabled on the target, get tpl/u-boot-tpl-dtb.bin or tpl/u-boot-tpl.bin
      if CONFIG_TPL_OF_CONTROL not enabled)

Writing to the board with USB
=============================

For USB to work you must get your board into ROM boot mode, either by erasing
your MMC or (perhaps) holding the recovery button when you boot the board.
To erase your MMC, you can boot into Linux and type (as root)

   dd if=/dev/zero of=/dev/mmcblk0 bs=1M

Connect your board's OTG port to your computer.

To create a suitable image and write it to the board:

   ./firefly-rk3288/tools/mkimage -n rk3288 -T rkimage -d \
	./firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
   cat out | openssl rc4 -K 7c4e0304550509072d2c7b38170d1711 | rkflashtool l

If all goes well you should something like:

   U-Boot SPL 2015.07-rc1-00383-ge345740-dirty (Jun 03 2015 - 10:06:49)
   Card did not respond to voltage select!
   spl: mmc init failed with error: -17
   ### ERROR ### Please RESET the board ###

You will need to reset the board before each time you try. Yes, that's all
it does so far. If support for the Rockchip USB protocol or DFU were added
in SPL then we could in principle load U-Boot and boot to a prompt from USB
as several other platforms do. However it does not seem to be possible to
use the existing boot ROM code from SPL.


Writing to the eMMC with USB on ROC-RK3308-CC
=============================================
For USB to work you must get your board into Bootrom mode,
either by erasing the eMMC or short circuit the GND and D0
on core board.

Connect the board to your computer via tyepc.
=> rkdeveloptool db rk3308_loader_v1.26.117.bin
=> rkdeveloptool wl 0x40 idbloader.img
=> rkdeveloptool wl 0x4000 u-boot.itb
=> rkdeveloptool rd

Then you will see the boot log from Debug UART at baud rate 1500000:
DDR Version V1.26
REGFB: 0x00000032, 0x00000032
In
589MHz
DDR3
 Col=10 Bank=8 Row=14 Size=256MB
msch:1
Returning to boot ROM...

U-Boot SPL 2020.01-rc1-00225-g34b681327f (Nov 14 2019 - 10:58:04 +0800)
Trying to boot from MMC1
INFO:    Preloader serial: 2
NOTICE:  BL31: v1.3(release):30f1405
NOTICE:  BL31: Built : 17:08:28, Sep 23 2019
INFO:    Lastlog: last=0x100000, realtime=0x102000, size=0x2000
INFO:    ARM GICv2 driver initialized
INFO:    Using opteed sec cpu_context!
INFO:    boot cpu mask: 1
INFO:    plat_rockchip_pmu_init: pd status 0xe b
INFO:    BL31: Initializing runtime services
WARNING: No OPTEE provided by BL2 boot loader, Booting device without OPTEE initialization. SMC`s destined for OPTEE will rK
ERROR:   Error initializing runtime service opteed_fast
INFO:    BL31: Preparing for EL3 exit to normal world
INFO:    Entry point address = 0x600000
INFO:    SPSR = 0x3c9


U-Boot 2020.01-rc1-00225-g34b681327f (Nov 14 2019 - 10:58:47 +0800)

Model: Firefly ROC-RK3308-CC board
DRAM:  254 MiB
MMC:   dwmmc@ff480000: 0, dwmmc@ff490000: 1
rockchip_dnl_key_pressed read adc key val failed
Net:   No ethernet found.
Hit any key to stop autoboot:  0
Card did not respond to voltage select!
switch to partitions #0, OK
mmc1(part 0) is current device
Scanning mmc 1:4...
Found /extlinux/extlinux.conf
Retrieving file: /extlinux/extlinux.conf
151 bytes read in 3 ms (48.8 KiB/s)
1:      kernel-mainline
Retrieving file: /Image
14737920 bytes read in 377 ms (37.3 MiB/s)
append: earlycon=uart8250,mmio32,0xff0c0000 console=ttyS2,1500000n8
Retrieving file: /rk3308-roc-cc.dtb
28954 bytes read in 4 ms (6.9 MiB/s)
Flattened Device Tree blob at 01f00000
Booting using the fdt blob at 0x1f00000
## Loading Device Tree to 000000000df3a000, end 000000000df44119 ... OK

Starting kernel ...
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd042]
[    0.000000] Linux version 5.4.0-rc1-00040-g4dc2d508fa47-dirty (andy@B150) (gcc version 6.3.1 20170404 (Linaro GCC 6.3-209
[    0.000000] Machine model: Firefly ROC-RK3308-CC board
[    0.000000] earlycon: uart8250 at MMIO32 0x00000000ff0c0000 (options '')
[    0.000000] printk: bootconsole [uart8250] enabled

Booting from an SD card
=======================

To write an image that boots from an SD card (assumed to be /dev/sdc):

   ./firefly-rk3288/tools/mkimage -n rk3288 -T rksd -d \
	firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
   sudo dd if=out of=/dev/sdc seek=64 && \
   sudo dd if=firefly-rk3288/u-boot-dtb.img of=/dev/sdc seek=16384

This puts the Rockchip header and SPL image first and then places the U-Boot
image at block 16384 (i.e. 8MB from the start of the SD card). This
corresponds with this setting in U-Boot:

   #define CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR	0x4000

Put this SD (or micro-SD) card into your board and reset it. You should see
something like:

   U-Boot 2016.01-rc2-00309-ge5bad3b-dirty (Jan 02 2016 - 23:41:59 -0700)

   Model: Radxa Rock 2 Square
   DRAM:  2 GiB
   MMC:   dwmmc@ff0f0000: 0, dwmmc@ff0c0000: 1
   *** Warning - bad CRC, using default environment

   In:    serial
   Out:   vop@ff940000.vidconsole
   Err:   serial
   Net:   Net Initialization Skipped
   No ethernet found.
   Hit any key to stop autoboot:  0
   =>

The rockchip bootrom can load and boot an initial spl, then continue to
load a second-stage bootloader (ie. U-Boot) as soon as the control is returned
to the bootrom. Both the RK3288 and the RK3036 use this special boot sequence.
The configuration option enabling this is:

	CONFIG_SPL_ROCKCHIP_BACK_TO_BROM=y

You can create the image via the following operations:

   ./firefly-rk3288/tools/mkimage -n rk3288 -T rksd -d \
	firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
   cat firefly-rk3288/u-boot-dtb.bin >> out && \
   sudo dd if=out of=/dev/sdc seek=64

If you have an HDMI cable attached you should see a video console.

For evb_rk3036 board:
	./evb-rk3036/tools/mkimage -n rk3036 -T rksd  -d evb-rk3036/spl/u-boot-spl.bin out && \
	cat evb-rk3036/u-boot-dtb.bin >> out && \
	sudo dd if=out of=/dev/sdc seek=64

Note: rk3036 SDMMC and debug uart use the same iomux, so if you boot from SD, the
      debug uart must be disabled


Booting from an SD card on RK3288 with TPL
==========================================

Since the size of SPL can't be exceeded 0x8000 bytes in RK3288, it is not possible add
new SPL features like Falcon mode or etc.

So introduce TPL so-that adding new features to SPL is possible because now TPL should
run minimal with code like DDR, clock etc and rest of new features in SPL.

As of now TPL is added on Vyasa-RK3288 board.

To write an image that boots from an SD card (assumed to be /dev/mmcblk0):

    sudo dd if=idbloader.img of=/dev/mmcblk0 seek=64 &&
    sudo dd if=u-boot-dtb.img of=/dev/mmcblk0 seek=16384

Booting from an SD card on RK3188
=================================

For rk3188 boards the general storage onto the card stays the same as
described above, but the image creation needs a bit more care.

The bootrom of rk3188 expects to find a small 1kb loader which returns
control to the bootrom, after which it will load the real loader, which
can then be up to 29kb in size and does the regular ddr init.  This is
handled by a single image (built as the SPL stage) that tests whether
it is handled for the first or second time via code executed from the
boot0-hook.

Additionally the rk3188 requires everything the bootrom loads to be
rc4-encrypted. Except for the very first stage the bootrom always reads
and decodes 2kb pages, so files should be sized accordingly.

# copy tpl, pad to 1020 bytes and append spl
tools/mkimage -n rk3188 -T rksd -d spl/u-boot-spl.bin out

# truncate, encode and append u-boot.bin
truncate -s %2048 u-boot.bin
cat u-boot.bin | split -b 512 --filter='openssl rc4 -K 7C4E0304550509072D2C7B38170D1711' >> out

Booting from an SD card on Pine64 Rock64 (RK3328)
=================================================

For Rock64 rk3328 board the following three parts are required:
TPL, SPL, and the u-boot image tree blob.

  - Write TPL/SPL image at 64 sector

    => sudo dd if=idbloader.img of=/dev/mmcblk0 seek=64

  - Write u-boot image tree blob at 16384 sector

    => sudo dd if=u-boot.itb of=/dev/mmcblk0 seek=16384

Booting from an SD card on RK3399
=================================

To write an image that boots from an SD card (assumed to be /dev/sdc):

Option 1: Package the image with Rockchip miniloader:

  - Create idbloader.img

    => cd /path/to/u-boot
    => ./tools/mkimage  -n rk3399 -T rksd -d /path/to/rkbin/bin/rk33/rk3399_ddr_800MHz_v1.20.bin idbloader.img
    => cat /path/to/rkbin/bin/rk33/rk3399_miniloader_v1.19.bin >> idbloader.img

  - Write idbloader.img at 64 sector

    => sudo dd if=idbloader.img of=/dev/sdc seek=64

  - Write trust.img at 24576

    => sudo dd if=trust.img of=/dev/sdc seek=24576

  - Write uboot.img at 16384 sector

    => sudo dd if=uboot.img of=/dev/sdc seek=16384
    => sync

Put this SD (or micro-SD) card into your board and reset it. You should see
something like:

DDR Version 1.20 20190314
In
Channel 0: DDR3, 933MHz
Bus Width=32 Col=10 Bank=8 Row=15 CS=1 Die Bus-Width=16 Size=1024MB
no stride
ch 0 ddrconfig = 0x101, ddrsize = 0x20
pmugrf_os_reg[2] = 0x10006281, stride = 0x17
OUT
Boot1: 2019-03-14, version: 1.19
CPUId = 0x0
ChipType = 0x10, 239
mmc: ERROR: SDHCI ERR:cmd:0x102,stat:0x18000
mmc: ERROR: Card did not respond to voltage select!
emmc reinit
mmc: ERROR: SDHCI ERR:cmd:0x102,stat:0x18000
mmc: ERROR: Card did not respond to voltage select!
emmc reinit
mmc: ERROR: SDHCI ERR:cmd:0x102,stat:0x18000
mmc: ERROR: Card did not respond to voltage select!
SdmmcInit=2 1
mmc0:cmd5,20
SdmmcInit=0 0
BootCapSize=0
UserCapSize=60543MB
FwPartOffset=2000 , 0
StorageInit ok = 45266
SecureMode = 0
SecureInit read PBA: 0x4
SecureInit read PBA: 0x404
SecureInit read PBA: 0x804
SecureInit read PBA: 0xc04
SecureInit read PBA: 0x1004
SecureInit read PBA: 0x1404
SecureInit read PBA: 0x1804
SecureInit read PBA: 0x1c04
SecureInit ret = 0, SecureMode = 0
atags_set_bootdev: ret:(0)
GPT 0x3380ec0 signature is wrong
recovery gpt...
GPT 0x3380ec0 signature is wrong
recovery gpt fail!
LoadTrust Addr:0x4000
No find bl30.bin
Load uboot, ReadLba = 2000
hdr 0000000003380880 + 0x0:0x88,0x41,0x3e,0x97,0xe6,0x61,0x54,0x23,0xe9,0x5a,0xd1,0x2b,0xdc,0x2f,0xf9,0x35,

Load OK, addr=0x200000, size=0x9c9c0
RunBL31 0x10000
NOTICE:  BL31: v1.3(debug):370ab80
NOTICE:  BL31: Built : 09:23:41, Mar  4 2019
NOTICE:  BL31: Rockchip release version: v1.1
INFO:    GICv3 with legacy support detected. ARM GICV3 driver initialized in EL3
INFO:    Using opteed sec cpu_context!
INFO:    boot cpu mask: 0
INFO:    plat_rockchip_pmu_init(1181): pd status 3e
INFO:    BL31: Initializing runtime services
INFO:    BL31: Initializing BL32
INF [0x0] TEE-CORE:init_primary_helper:337: Initializing (1.1.0-195-g8f090d20 #6 Fri Dec  7 06:11:20 UTC 2018 aarch64)

INF [0x0] TEE-CORE:init_primary_helper:338: Release version: 1.2

INF [0x0] TEE-CORE:init_teecore:83: teecore inits done
INFO:    BL31: Preparing for EL3 exit to normal world
INFO:    Entry point address = 0x200000
INFO:    SPSR = 0x3c9


U-Boot 2019.04-rc4-00136-gfd121f9641-dirty (Apr 16 2019 - 14:02:47 +0530)

Model: FriendlyARM NanoPi NEO4
DRAM:  1022 MiB
MMC:   dwmmc@fe310000: 2, dwmmc@fe320000: 1, sdhci@fe330000: 0
Loading Environment from MMC... *** Warning - bad CRC, using default environment

In:    serial@ff1a0000
Out:   serial@ff1a0000
Err:   serial@ff1a0000
Model: FriendlyARM NanoPi NEO4
Net:   eth0: ethernet@fe300000
Hit any key to stop autoboot:  0
=>

Option 2: Package the image with SPL:

  - Prefix rk3399 header to SPL image

    => cd /path/to/u-boot
    => ./tools/mkimage -n rk3399 -T rksd -d spl/u-boot-spl-dtb.bin out

  - Write prefixed SPL at 64th sector

    => sudo dd if=out of=/dev/sdc seek=64

  - Write U-Boot proper at 16384 sector

    => sudo dd if=u-boot.itb of=/dev/sdc seek=16384
    => sync

Put this SD (or micro-SD) card into your board and reset it. You should see
something like:

U-Boot SPL board init
Trying to boot from MMC1


U-Boot 2019.01-00004-g14db5ee998 (Mar 11 2019 - 13:18:41 +0530)

Model: Orange Pi RK3399 Board
DRAM:  2 GiB
MMC:   dwmmc@fe310000: 2, dwmmc@fe320000: 1, sdhci@fe330000: 0
Loading Environment from MMC... OK
In:    serial@ff1a0000
Out:   serial@ff1a0000
Err:   serial@ff1a0000
Model: Orange Pi RK3399 Board
Net:   eth0: ethernet@fe300000
Hit any key to stop autoboot:  0
=>

Option 3: Package the image with TPL:

  - Write tpl+spl at 64th sector

    => sudo dd if=idbloader.img of=/dev/sdc seek=64

  - Write U-Boot proper at 16384 sector

    => sudo dd if=u-boot.itb of=/dev/sdc seek=16384
    => sync

Put this SD (or micro-SD) card into your board and reset it. You should see
something like:

U-Boot TPL board init
Trying to boot from BOOTROM
Returning to boot ROM...

U-Boot SPL board init
Trying to boot from MMC1


U-Boot 2019.07-rc1-00241-g5b3244767a (May 08 2019 - 10:51:06 +0530)

Model: Orange Pi RK3399 Board
DRAM:  2 GiB
MMC:   dwmmc@fe310000: 2, dwmmc@fe320000: 1, sdhci@fe330000: 0
Loading Environment from MMC... OK
In:    serial@ff1a0000
Out:   serial@ff1a0000
Err:   serial@ff1a0000
Model: Orange Pi RK3399 Board
Net:   eth0: ethernet@fe300000
Hit any key to stop autoboot:  0
=>

Using fastboot on rk3288
========================
- Write GPT partition layout to mmc device which fastboot want to use it to
store the image

        => gpt write mmc 1 $partitions

- Invoke fastboot command to prepare

        => fastboot 1

- Start fastboot request on PC

        fastboot -i 0x2207 flash loader evb-rk3288/spl/u-boot-spl-dtb.bin

You should see something like:

        => fastboot 1
        WARNING: unknown variable: partition-type:loader
        Starting download of 357796 bytes
        ..
        downloading of 357796 bytes finished
        Flashing Raw Image
        ........ wrote 357888 bytes to 'loader'

Booting from SPI
================

To write an image that boots from SPI flash (e.g. for the Haier Chromebook or
Bob):

   ./chromebook_jerry/tools/mkimage -n rk3288 -T rkspi \
	-d chromebook_jerry/spl/u-boot-spl-dtb.bin spl.bin && \
   dd if=spl.bin of=spl-out.bin bs=128K conv=sync && \
   cat spl-out.bin chromebook_jerry/u-boot-dtb.img >out.bin && \
   dd if=out.bin of=out.bin.pad bs=4M conv=sync

This converts the SPL image to the required SPI format by adding the Rockchip
header and skipping every second 2KB block. Then the U-Boot image is written at
offset 128KB and the whole image is padded to 4MB which is the SPI flash size.
The position of U-Boot is controlled with this setting in U-Boot:

   #define CONFIG_SYS_SPI_U_BOOT_OFFS	0x20000

If you have a Dediprog em100pro connected then you can write the image with:

      sudo em100 -s -c GD25LQ32 -d out.bin.pad -r

When booting you should see something like:

   U-Boot SPL 2015.07-rc2-00215-g9a58220-dirty (Jun 23 2015 - 12:11:32)


   U-Boot 2015.07-rc2-00215-g9a58220-dirty (Jun 23 2015 - 12:11:32 -0600)

   Model: Google Jerry
   DRAM:  2 GiB
   MMC:
   Using default environment

   In:    serial@ff690000
   Out:   serial@ff690000
   Err:   serial@ff690000
   =>

Future work
===========

Immediate priorities are:

- USB host
- USB device
- Run CPU at full speed (code exists but we only see ~60 DMIPS maximum)
- NAND flash
- Boot U-Boot proper over USB OTG (at present only SPL works)


Development Notes
=================

There are plenty of patches in the links below to help with this work.

[1] https://github.com/rkchrome/uboot.git
[2] https://github.com/linux-rockchip/u-boot-rockchip.git branch u-boot-rk3288
[3] https://github.com/linux-rockchip/rkflashtool.git
[4] http://wiki.t-firefly.com/index.php/Firefly-RK3288/Serial_debug/en

rkimage
-------

rkimage.c produces an SPL image suitable for sending directly to the boot ROM
over USB OTG. This is a very simple format - just the string RK32 (as 4 bytes)
followed by u-boot-spl-dtb.bin.

The boot ROM loads image to 0xff704000 which is in the internal SRAM. The SRAM
starts at 0xff700000 and extends to 0xff718000 where we put the stack.

rksd
----

rksd.c produces an image consisting of 32KB of empty space, a header and
u-boot-spl-dtb.bin. The header is defined by 'struct header0_info' although
most of the fields are unused by U-Boot. We just need to specify the
signature, a flag and the block offset and size of the SPL image.

The header occupies a single block but we pad it out to 4 blocks. The header
is encoding using RC4 with the key 7c4e0304550509072d2c7b38170d1711. The SPL
image can be encoded too but we don't do that.

The maximum size of u-boot-spl-dtb.bin which the boot ROM will read is 32KB,
or 0x40 blocks. This is a severe and annoying limitation. There may be a way
around this limitation, since there is plenty of SRAM, but at present the
board refuses to boot if this limit is exceeded.

The image produced is padded up to a block boundary (512 bytes). It should be
written to the start of an SD card using dd.

Since this image is set to load U-Boot from the SD card at block offset,
CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR, dd should be used to write
u-boot-dtb.img to the SD card at that offset. See above for instructions.

rkspi
-----

rkspi.c produces an image consisting of a header and u-boot-spl-dtb.bin. The
resulting image is then spread out so that only the first 2KB of each 4KB
sector is used. The header is the same as with rksd and the maximum size is
also 32KB (before spreading). The image should be written to the start of
SPI flash.

See above for instructions on how to write a SPI image.

rkmux.py
--------

You can use this script to create #defines for SoC register access. See the
script for usage.


Device tree and driver model
----------------------------

Where possible driver model is used to provide a structure to the
functionality. Device tree is used for configuration. However these have an
overhead and in SPL with a 32KB size limit some shortcuts have been taken.
In general all Rockchip drivers should use these features, with SPL-specific
modifications where required.

GPT partition layout
----------------------------

Rockchip use a unified GPT partition layout  in open source support.
With this GPT partition layout, uboot can be compatilbe with other components,
like miniloader, trusted-os, arm-trust-firmware.

There are some documents about partitions in the links below.
http://rockchip.wikidot.com/partitions

--
Jagan Teki <jagan@amarulasolutions.com>
27 Mar 2019
Simon Glass <sjg@chromium.org>
24 June 2015