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Summary
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=======
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This document covers various features of the 'am335x_evm' build, and some of
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the related build targets (am335x_evm_uartN, etc).
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Hardware
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========
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The binary produced by this board supports, based on parsing of the EEPROM
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documented in TI's reference designs:
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- AM335x GP EVM
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- AM335x EVM SK
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- Beaglebone White
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- Beaglebone Black
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Customization
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=============
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Given that all of the above boards are reference platforms (and the
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Beaglebone platforms are OSHA), it is likely that this platform code and
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configuration will be used as the basis of a custom platform. It is
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worth noting that aside from things such as NAND or MMC only being
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required if a custom platform makes use of these blocks, the following
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are required, depending on design:
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- GPIO is only required if DDR3 power is controlled in a way similar to
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EVM SK
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- SPI is only required for SPI flash, or exposing the SPI bus.
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The following blocks are required:
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- I2C, to talk with the PMIC and ensure that we do not run afoul of
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errata 1.0.24.
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When removing options as part of customization,
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CONFIG_EXTRA_ENV_SETTINGS will need additional care to update for your
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needs and to remove no longer relevant options as in some cases we
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define additional text blocks (such as for NAND or DFU strings). Also
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note that all of the SPL options are grouped together, rather than with
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the IP blocks, so both areas will need their choices updated to reflect
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the custom design.
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NAND
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====
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The AM335x GP EVM ships with a 256MiB NAND available in most profiles. In
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this example to program the NAND we assume that an SD card has been
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inserted with the files to write in the first SD slot and that mtdparts
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have been configured correctly for the board. All images are first loaded
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into memory, then written to NAND.
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Step-1: Building u-boot for NAND boot
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Set following CONFIGxx options for NAND device.
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CONFIG_SYS_NAND_PAGE_SIZE number of main bytes in NAND page
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CONFIG_SYS_NAND_OOBSIZE number of OOB bytes in NAND page
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CONFIG_SYS_NAND_BLOCK_SIZE number of bytes in NAND erase-block
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CONFIG_SYS_NAND_ECCPOS ECC map for NAND page
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CONFIG_NAND_OMAP_ECCSCHEME (refer doc/README.nand)
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Step-2: Flashing NAND via MMC/SD
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# select BOOTSEL to MMC/SD boot and boot from MMC/SD card
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U-Boot # mmc rescan
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# erase flash
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U-Boot # nand erase.chip
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U-Boot # env default -f -a
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U-Boot # saveenv
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# flash MLO. Redundant copies of MLO are kept for failsafe
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U-Boot # load mmc 0 0x82000000 MLO
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U-Boot # nand write 0x82000000 0x00000 0x20000
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U-Boot # nand write 0x82000000 0x20000 0x20000
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U-Boot # nand write 0x82000000 0x40000 0x20000
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U-Boot # nand write 0x82000000 0x60000 0x20000
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# flash u-boot.img
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U-Boot # load mmc 0 0x82000000 u-boot.img
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U-Boot # nand write 0x82000000 0x80000 0x60000
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# flash kernel image
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U-Boot # load mmc 0 0x82000000 uImage
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U-Boot # nand write 0x82000000 ${nandsrcaddr} ${nandimgsize}
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# flash filesystem image
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U-Boot # load mmc 0 0x82000000 filesystem.img
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U-Boot # nand write 0x82000000 ${loadaddress} 0x300000
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Step-3: Set BOOTSEL pin to select NAND boot, and POR the device.
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The device should boot from images flashed on NAND device.
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NOR
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===
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The Beaglebone White can be equiped with a "memory cape" that in turn can
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have a NOR module plugged into it. In this case it is then possible to
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program and boot from NOR. Note that due to how U-Boot is architectured we
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must build a specific version of U-Boot that knows we have NOR flash. This
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build is named 'am335x_evm_nor'. Further, we have a 'am335x_evm_norboot'
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build that will assume that the environment is on NOR rather than NAND. In
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the following example we assume that and SD card has been populated with
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MLO and u-boot.img from a 'am335x_evm_nor' build and also contains the
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'u-boot.bin' from a 'am335x_evm_norboot' build. When booting from NOR, a
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binary must be written to the start of NOR, with no header or similar
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prepended. In the following example we use a size of 512KiB (0x80000)
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as that is how much space we set aside before the environment, as per
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the config file.
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U-Boot # mmc rescan
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U-Boot # load mmc 0 ${loadaddr} u-boot.bin
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U-Boot # protect off 08000000 +80000
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U-Boot # erase 08000000 +80000
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U-Boot # cp.b ${loadaddr} 08000000 ${filesize}
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Falcon Mode
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===========
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The default build includes "Falcon Mode" (see doc/README.falcon) via NAND,
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eMMC (or raw SD cards) and FAT SD cards. Our default behavior currently is
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to read a 'c' on the console while in SPL at any point prior to loading the
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OS payload (so as soon as possible) to opt to booting full U-Boot. Also
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note that while one can program Falcon Mode "in place" great care needs to
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be taken by the user to not 'brick' their setup. As these are all eval
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boards with multiple boot methods, recovery should not be an issue in this
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worst-case however.
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Falcon Mode: eMMC
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=================
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The recommended layout in this case is:
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MMC BLOCKS |--------------------------------| LOCATION IN BYTES
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0x0000 - 0x007F : MBR or GPT table : 0x000000 - 0x020000
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0x0080 - 0x00FF : ARGS or FDT file : 0x010000 - 0x020000
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0x0100 - 0x01FF : SPL.backup1 (first copy used) : 0x020000 - 0x040000
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0x0200 - 0x02FF : SPL.backup2 (second copy used) : 0x040000 - 0x060000
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0x0300 - 0x06FF : U-Boot : 0x060000 - 0x0e0000
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0x0700 - 0x08FF : U-Boot Env + Redundant : 0x0e0000 - 0x120000
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0x0900 - 0x28FF : Kernel : 0x120000 - 0x520000
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Note that when we run 'spl export' it will prepare to boot the kernel.
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This includes relocation of the uImage from where we loaded it to the entry
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point defined in the header. As these locations overlap by default, it
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would leave us with an image that if written to MMC will not boot, so
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instead of using the loadaddr variable we use 0x81000000 in the following
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example. In this example we are loading from the network, for simplicity,
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and assume a valid partition table already exists and 'mmc dev' has already
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been run to select the correct device. Also note that if you previously
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had a FAT partition (such as on a Beaglebone Black) it is not enough to
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write garbage into the area, you must delete it from the partition table
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first.
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# Ensure we are able to talk with this mmc device
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U-Boot # mmc rescan
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U-Boot # tftp 81000000 am335x/MLO
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# Write to two of the backup locations ROM uses
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U-Boot # mmc write 81000000 100 100
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U-Boot # mmc write 81000000 200 100
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# Write U-Boot to the location set in the config
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U-Boot # tftp 81000000 am335x/u-boot.img
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U-Boot # mmc write 81000000 300 400
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# Load kernel and device tree into memory, perform export
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U-Boot # tftp 81000000 am335x/uImage
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U-Boot # run findfdt
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U-Boot # tftp ${fdtaddr} am335x/${fdtfile}
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U-Boot # run mmcargs
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U-Boot # spl export fdt 81000000 - ${fdtaddr}
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# Write the updated device tree to MMC
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U-Boot # mmc write ${fdtaddr} 80 80
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# Write the uImage to MMC
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U-Boot # mmc write 81000000 900 2000
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Falcon Mode: FAT SD cards
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=========================
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In this case the additional file is written to the filesystem. In this
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example we assume that the uImage and device tree to be used are already on
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the FAT filesystem (only the uImage MUST be for this to function
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afterwards) along with a Falcon Mode aware MLO and the FAT partition has
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already been created and marked bootable:
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U-Boot # mmc rescan
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# Load kernel and device tree into memory, perform export
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U-Boot # load mmc 0:1 ${loadaddr} uImage
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U-Boot # run findfdt
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U-Boot # load mmc 0:1 ${fdtaddr} ${fdtfile}
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U-Boot # run mmcargs
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U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
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This will print a number of lines and then end with something like:
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Using Device Tree in place at 80f80000, end 80f85928
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Using Device Tree in place at 80f80000, end 80f88928
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So then you:
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U-Boot # fatwrite mmc 0:1 0x80f80000 args 8928
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Falcon Mode: NAND
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=================
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In this case the additional data is written to another partition of the
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NAND. In this example we assume that the uImage and device tree to be are
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already located on the NAND somewhere (such as fileystem or mtd partition)
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along with a Falcon Mode aware MLO written to the correct locations for
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booting and mtdparts have been configured correctly for the board:
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U-Boot # nand read ${loadaddr} kernel
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U-Boot # load nand rootfs ${fdtaddr} /boot/am335x-evm.dtb
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U-Boot # run nandargs
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U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
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U-Boot # nand erase.part u-boot-spl-os
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U-Boot # nand write ${fdtaddr} u-boot-spl-os
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