On Sep 23, 2009, at 2:20 AM, Mingkai Hu wrote:
MPC8536E can support booting from NAND flash which uses the image u-boot-nand.bin. This image contains two parts: a 4K NAND loader and a main U-Boot image. The former is appended to the latter to produce u-boot-nand.bin. The 4K NAND loader includes the corresponding nand_spl directory, along with the code twisted by CONFIG_NAND_SPL. The main U-Boot image just like a general U-Boot image except the parts that included by CONFIG_SYS_RAMBOOT.
When power on, eLBC will automatically load from bank 0 the 4K NAND loader into the FCM buffer RAM where CPU can execute the boot code directly. In the first stage, the NAND loader copies itself to RAM or L2SRAM to free up the FCM buffer RAM, then loads the main image from NAND flash to RAM or L2SRAM and boot from it.
This patch implements the NAND loader to load the main image into L2SRAM, so the main image can configure the RAM by using SPD EEPROM. In the first stage, the NAND loader copies itself to the second to last 4K address space, and uses the last 4K address space as the initial RAM for stack.
Obviously, the size of L2SRAM shouldn't be less than the size of the image used. If so, the workaround is to generate another image that includes the code to configure the RAM by SPD and load it to L2SRAM first, then relocate the main image to RAM to boot up.
Signed-off-by: Mingkai Hu Mingkai.hu@freescale.com
Change over v3:
- Intergrated Scott's comments.
- Intergrated Wolfgang's comments.
applied to 85xx
- k