94 lines
3.3 KiB
Plaintext
94 lines
3.3 KiB
Plaintext
Summary
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=======
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The README is for the boot procedure used for TI's OMAP-L138 based
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hawkboard. The hawkboard comes with a 128MiB Nand flash and a 128MiB
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DDR SDRAM along with a host of other controllers.
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The hawkboard is booted in three stages. The initial bootloader which
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executes upon reset is the Rom Boot Loader(RBL) which sits in the
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internal ROM of the omap. The RBL initialises the memory and the nand
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controller, and copies the image stored at a predefined location(block
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1) of the nand flash. The image loaded by the RBL to the memory is the
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AIS signed nand_spl image. This, in turns copies the u-boot binary
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from the nand flash to the memory and jumps to the u-boot entry point.
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AIS is an image format defined by TI for the images that are to be
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loaded to memory by the RBL. The image is divided into a series of
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sections and the image's entry point is specified. Each section comes
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with meta data like the target address the section is to be copied to
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and the size of the section, which is used by the RBL to load the
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image. At the end of the image the RBL jumps to the image entry
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point.
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The secondary stage bootloader(nand_spl) which is loaded by the RBL
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then loads the u-boot from a predefined location in the nand to the
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memory and jumps to the u-boot entry point.
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The reason a secondary stage bootloader is used is because the ECC
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layout expected by the RBL is not the same as that used by
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u-boot/linux. This also implies that for flashing the nand_spl image,
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we need to use the u-boot which uses the ECC layout expected by the
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RBL[1]. Booting u-boot over UART(UART boot) is explained here[2].
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Compilation
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===========
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Three images might be needed
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* nand_spl - This is the secondary bootloader which boots the u-boot
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binary.
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hawkboard_nand_config
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The nand_spl ELF gets generated under nand_spl/u-boot-spl. This
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needs to be processed with the AISGen tool for generating the AIS
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signed image to be flashed. Steps for generating the AIS image are
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explained here[3].
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* u-boot binary - This is the image flashed to the nand and copied to
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the memory by the nand_spl.
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hawkboard_config
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* u-boot for uart boot - This is same as the u-boot binary generated
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above, with the sole difference of the CONFIG_SYS_TEXT_BASE being
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0xc1080000, as expected by the RBL.
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hawkboard_uart_config
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Flashing the images to Nand
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===========================
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The nand_spl AIS image needs to be flashed to the block 1 of the
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Nand flash, as that is the location the RBL expects the image[4]. For
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flashing the nand_spl, boot over the u-boot specified in [1], and
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flash the image
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=> tftpboot 0xc0700000 <nand_spl_ais.bin>
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=> nand erase 0x20000 0x20000
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=> nand write.e 0xc0700000 0x20000 <nand_spl_size>
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The u-boot binary is flashed at location 0xe0000(block 6) of the nand
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flash. The nand_spl loader expects the u-boot at this location. For
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flashing the u-boot binary
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=> tftpboot 0xc0700000 u-boot.bin
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=> nand erase 0xe0000 0x40000
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=> nand write.e 0xc0700000 0xe0000 <u-boot-size>
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Links
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=====
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[1]
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http://code.google.com/p/hawkboard/downloads/detail?name=u-boot_uart_ais_v1.bin
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[2]
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http://elinux.org/Hawkboard#Booting_u-boot_over_UART
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[3]
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http://elinux.org/Hawkboard#Signing_u-boot_for_UART_boot
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[4]
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http://processors.wiki.ti.com/index.php/RBL_UBL_and_host_program#RBL_booting_from_NAND_and_ECC.2FBad_blocks
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