| .. SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause |
| .. sectionauthor:: Tom Rini <trini@konsulko.com> |
| |
| AM335x Generation |
| ================= |
| |
| Summary |
| ------- |
| |
| This document covers various features of the `am335x_evm` default |
| configuration, some of the related defconfigs, and how to enable hardware |
| features not present by default in the defconfigs. |
| |
| Hardware |
| -------- |
| |
| The binary produced by this board supports, based on parsing of the EEPROM |
| documented in TI's reference designs: |
| * AM335x GP EVM |
| * AM335x EVM SK |
| * The Beaglebone family of designs |
| |
| Customization |
| ------------- |
| |
| Given that all of the above boards are reference platforms (and the |
| Beaglebone platforms are OSHA), it is likely that this platform code and |
| configuration will be used as the basis of a custom platform. It is |
| worth noting that aside from things such as NAND or MMC only being |
| required if a custom platform makes use of these blocks, the following |
| are required, depending on design: |
| |
| * GPIO is only required if DDR3 power is controlled in a way similar to EVM SK |
| * SPI is only required for SPI flash, or exposing the SPI bus. |
| |
| The following blocks are required: |
| |
| * I2C, to talk with the PMIC and ensure that we do not run afoul of |
| errata 1.0.24. |
| |
| When removing options as part of customization, note that you will likely need |
| to look at both `include/configs/am335x_evm.h`, |
| `include/configs/ti_am335x_common.h` and `include/configs/am335x_evm.h` as the |
| migration to Kconfig is not yet complete. |
| |
| NAND |
| ---- |
| |
| The AM335x GP EVM ships with a 256MiB NAND available in most profiles. In |
| this example to program the NAND we assume that an SD card has been |
| inserted with the files to write in the first SD slot and that mtdparts |
| have been configured correctly for the board. All images are first loaded |
| into memory, then written to NAND. |
| |
| Step-1: Building u-boot for NAND boot |
| Set following CONFIGxx options for NAND device. |
| CONFIG_SYS_NAND_PAGE_SIZE number of main bytes in NAND page |
| CONFIG_SYS_NAND_OOBSIZE number of OOB bytes in NAND page |
| CONFIG_SYS_NAND_BLOCK_SIZE number of bytes in NAND erase-block |
| CFG_SYS_NAND_ECCPOS ECC map for NAND page |
| CONFIG_NAND_OMAP_ECCSCHEME (refer doc/README.nand) |
| |
| Step-2: Flashing NAND via MMC/SD |
| |
| .. code-block:: text |
| |
| # select BOOTSEL to MMC/SD boot and boot from MMC/SD card |
| U-Boot # mmc rescan |
| # erase flash |
| U-Boot # nand erase.chip |
| U-Boot # env default -f -a |
| U-Boot # saveenv |
| # flash MLO. Redundant copies of MLO are kept for failsafe |
| U-Boot # load mmc 0 0x82000000 MLO |
| U-Boot # nand write 0x82000000 0x00000 0x20000 |
| U-Boot # nand write 0x82000000 0x20000 0x20000 |
| U-Boot # nand write 0x82000000 0x40000 0x20000 |
| U-Boot # nand write 0x82000000 0x60000 0x20000 |
| # flash u-boot.img |
| U-Boot # load mmc 0 0x82000000 u-boot.img |
| U-Boot # nand write 0x82000000 0x80000 0x60000 |
| # flash kernel image |
| U-Boot # load mmc 0 0x82000000 uImage |
| U-Boot # nand write 0x82000000 ${nandsrcaddr} ${nandimgsize} |
| # flash filesystem image |
| U-Boot # load mmc 0 0x82000000 filesystem.img |
| U-Boot # nand write 0x82000000 ${loadaddress} 0x300000 |
| |
| Step-3: Set BOOTSEL pin to select NAND boot, and POR the device. |
| The device should boot from images flashed on NAND device. |
| |
| |
| Falcon Mode |
| ----------- |
| |
| The default build includes "Falcon Mode" (see doc/README.falcon) via NAND, |
| eMMC (or raw SD cards) and FAT SD cards. Our default behavior currently is |
| to read a 'c' on the console while in SPL at any point prior to loading the |
| OS payload (so as soon as possible) to opt to booting full U-Boot. Also |
| note that while one can program Falcon Mode "in place" great care needs to |
| be taken by the user to not 'brick' their setup. As these are all eval |
| boards with multiple boot methods, recovery should not be an issue in this |
| worst-case however. |
| |
| Falcon Mode: eMMC |
| ----------------- |
| |
| The recommended layout in this case is: |
| |
| .. code-block:: text |
| |
| MMC BLOCKS |--------------------------------| LOCATION IN BYTES |
| 0x0000 - 0x007F : MBR or GPT table : 0x000000 - 0x020000 |
| 0x0080 - 0x00FF : ARGS or FDT file : 0x010000 - 0x020000 |
| 0x0100 - 0x01FF : SPL.backup1 (first copy used) : 0x020000 - 0x040000 |
| 0x0200 - 0x02FF : SPL.backup2 (second copy used) : 0x040000 - 0x060000 |
| 0x0300 - 0x06FF : U-Boot : 0x060000 - 0x0e0000 |
| 0x0700 - 0x08FF : U-Boot Env + Redundant : 0x0e0000 - 0x120000 |
| 0x0900 - 0x28FF : Kernel : 0x120000 - 0x520000 |
| |
| Note that when we run 'spl export' it will prepare to boot the kernel. |
| This includes relocation of the uImage from where we loaded it to the entry |
| point defined in the header. As these locations overlap by default, it |
| would leave us with an image that if written to MMC will not boot, so |
| instead of using the loadaddr variable we use 0x81000000 in the following |
| example. In this example we are loading from the network, for simplicity, |
| and assume a valid partition table already exists and 'mmc dev' has already |
| been run to select the correct device. Also note that if you previously |
| had a FAT partition (such as on a Beaglebone Black) it is not enough to |
| write garbage into the area, you must delete it from the partition table |
| first. |
| |
| .. code-block:: text |
| |
| # Ensure we are able to talk with this mmc device |
| U-Boot # mmc rescan |
| U-Boot # tftp 81000000 am335x/MLO |
| # Write to two of the backup locations ROM uses |
| U-Boot # mmc write 81000000 100 100 |
| U-Boot # mmc write 81000000 200 100 |
| # Write U-Boot to the location set in the config |
| U-Boot # tftp 81000000 am335x/u-boot.img |
| U-Boot # mmc write 81000000 300 400 |
| # Load kernel and device tree into memory, perform export |
| U-Boot # tftp 81000000 am335x/uImage |
| U-Boot # run findfdt |
| U-Boot # tftp ${fdtaddr} am335x/${fdtfile} |
| U-Boot # run mmcargs |
| U-Boot # spl export fdt 81000000 - ${fdtaddr} |
| # Write the updated device tree to MMC |
| U-Boot # mmc write ${fdtaddr} 80 80 |
| # Write the uImage to MMC |
| U-Boot # mmc write 81000000 900 2000 |
| |
| Falcon Mode: FAT SD cards |
| ------------------------- |
| |
| In this case the additional file is written to the filesystem. In this |
| example we assume that the uImage and device tree to be used are already on |
| the FAT filesystem (only the uImage MUST be for this to function |
| afterwards) along with a Falcon Mode aware MLO and the FAT partition has |
| already been created and marked bootable: |
| |
| .. code-block:: text |
| |
| U-Boot # mmc rescan |
| # Load kernel and device tree into memory, perform export |
| U-Boot # load mmc 0:1 ${loadaddr} uImage |
| U-Boot # run findfdt |
| U-Boot # load mmc 0:1 ${fdtaddr} ${fdtfile} |
| U-Boot # run mmcargs |
| U-Boot # spl export fdt ${loadaddr} - ${fdtaddr} |
| |
| This will print a number of lines and then end with something like: |
| |
| .. code-block:: text |
| |
| Using Device Tree in place at 80f80000, end 80f85928 |
| Using Device Tree in place at 80f80000, end 80f88928 |
| |
| So then you: |
| |
| .. code-block:: text |
| |
| U-Boot # fatwrite mmc 0:1 0x80f80000 args 8928 |
| |
| Falcon Mode: NAND |
| ----------------- |
| |
| In this case the additional data is written to another partition of the |
| NAND. In this example we assume that the uImage and device tree to be are |
| already located on the NAND somewhere (such as filesystem or mtd partition) |
| along with a Falcon Mode aware MLO written to the correct locations for |
| booting and mtdparts have been configured correctly for the board: |
| |
| .. code-block:: text |
| |
| U-Boot # nand read ${loadaddr} kernel |
| U-Boot # load nand rootfs ${fdtaddr} /boot/am335x-evm.dtb |
| U-Boot # run nandargs |
| U-Boot # spl export fdt ${loadaddr} - ${fdtaddr} |
| U-Boot # nand erase.part u-boot-spl-os |
| U-Boot # nand write ${fdtaddr} u-boot-spl-os |
| |
| USB device |
| ---------- |
| |
| The platform code for am33xx based designs is legacy in the sense that |
| it is not fully compliant with the driver model in its management of the |
| various resources. This is particularly true for the USB Ethernet gadget |
| which will automatically be bound to the first USB Device Controller |
| (UDC). This make the USB Ethernet gadget work out of the box on common |
| boards like the Beagle Bone Blacks and by default will prevents other |
| gadgets to be used. |
| |
| The output of the 'dm tree' command shows which driver is bound to which |
| device, so the user can easily configure their platform differently from |
| the command line: |
| |
| .. code-block:: text |
| |
| => dm tree |
| Class Index Probed Driver Name |
| ----------------------------------------------------------- |
| [...] |
| misc 0 [ + ] ti-musb-wrapper | |-- usb@47400000 |
| usb 0 [ + ] ti-musb-peripheral | | |-- usb@47401000 |
| ethernet 1 [ + ] usb_ether | | | `-- usb_ether |
| bootdev 3 [ ] eth_bootdev | | | `-- usb_ether.bootdev |
| usb 0 [ ] ti-musb-host | | `-- usb@47401800 |
| |
| Typically here any network command performed using the usb_ether |
| interface would work, while using other gadgets would fail: |
| |
| .. code-block:: text |
| |
| => fastboot usb 0 |
| All UDC in use (1 available), use the unbind command |
| g_dnl_register: failed!, error: -19 |
| exit not allowed from main input shell. |
| |
| As hinted by the primary error message, the only controller available |
| (usb@47401000) is currently bound to the usb_ether driver, which makes |
| it impossible for the fastboot command to bind with this device (at |
| least from a bootloader point of view). The solution here would be to |
| use the unbind command specifying the class and index parameters (as |
| shown above in the 'dm tree' output) to target the driver to unbind: |
| |
| .. code-block:: text |
| |
| => unbind ethernet 1 |
| |
| The output of the 'dm tree' command now shows the availability of the |
| first USB device controller, the fastboot gadget will now be able to |
| bind with it: |
| |
| .. code-block:: text |
| |
| => dm tree |
| Class Index Probed Driver Name |
| ----------------------------------------------------------- |
| [...] |
| misc 0 [ + ] ti-musb-wrapper | |-- usb@47400000 |
| usb 0 [ ] ti-musb-peripheral | | |-- usb@47401000 |
| usb 0 [ ] ti-musb-host | | `-- usb@47401800 |