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diff --git a/board/ti/am335x/README b/board/ti/am335x/README new file mode 100644 index 0000000..ccc5e16 --- /dev/null +++ b/board/ti/am335x/README @@ -0,0 +1,113 @@ +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 + +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 |