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- Summary
- =======
- This document covers various features of the 'am335x_evm' build, and some of
- the related build targets (am335x_evm_uartN, etc).
- 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
- - Beaglebone White
- - Beaglebone Black
- 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,
- CONFIG_EXTRA_ENV_SETTINGS will need additional care to update for your
- needs and to remove no longer relevant options as in some cases we
- define additional text blocks (such as for NAND or DFU strings). Also
- note that all of the SPL options are grouped together, rather than with
- the IP blocks, so both areas will need their choices updated to reflect
- the custom design.
- 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. As a time saving measure we
- load MLO into memory in one location, copy it into the three locatations
- that the ROM checks for additional valid copies, then load U-Boot into
- memory. We then write that whole section of memory to NAND.
- U-Boot # mmc rescan
- U-Boot # env default -f -a
- U-Boot # nand erase.chip
- U-Boot # saveenv
- U-Boot # load mmc 0 81000000 MLO
- U-Boot # cp.b 81000000 81020000 20000
- U-Boot # cp.b 81000000 81040000 20000
- U-Boot # cp.b 81000000 81060000 20000
- U-Boot # load mmc 0 81080000 u-boot.img
- U-Boot # nand write 81000000 0 260000
- U-Boot # load mmc 0 ${loadaddr} uImage
- U-Boot # nand write ${loadaddr} kernel 500000
- NOR
- ===
- The Beaglebone White can be equiped with a "memory cape" that in turn can
- have a NOR module plugged into it. In this case it is then possible to
- program and boot from NOR. Note that due to how U-Boot is architectured we
- must build a specific version of U-Boot that knows we have NOR flash. This
- build is named 'am335x_evm_nor'. Further, we have a 'am335x_evm_norboot'
- build that will assume that the environment is on NOR rather than NAND. In
- the following example we assume that and SD card has been populated with
- MLO and u-boot.img from a 'am335x_evm_nor' build and also contains the
- 'u-boot.bin' from a 'am335x_evm_norboot' build. When booting from NOR, a
- binary must be written to the start of NOR, with no header or similar
- prepended. In the following example we use a size of 512KiB (0x80000)
- as that is how much space we set aside before the environment, as per
- the config file.
- U-Boot # mmc rescan
- U-Boot # load mmc 0 ${loadaddr} u-boot.bin
- U-Boot # protect off 08000000 +80000
- U-Boot # erase 08000000 +80000
- U-Boot # cp.b ${loadaddr} 08000000 ${filesize}
- 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:
- 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.
- # 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:
- 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:
- Using Device Tree in place at 80f80000, end 80f85928
- Using Device Tree in place at 80f80000, end 80f88928
- So then you:
- 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 fileystem 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:
- 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
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