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