[U-Boot-Users] How to support multiple flash sizes ?

[Laurent Pinchart]

Hi,

I'm trying to find a way for U-Boot to automatically detect the flash base 
address.

Our custom board can be mounted with different flash options, from 16MB to 
128MB. I would like to avoid programming the board with a different boot 
loader for each flash size, so I was trying a way to create a 
"one-fits-them-all" U-Boot version.

I thought defining CFG_FLASH_BASE to 0xF8000000 would be enough, as the flash 
would repeat over the 128MB memory range. This indeed works fine for reading, 
but U-Boot is clever enough to detect the flash size, which leads to problems 
when erasing sectors. The environment, for instance, is stored at TEXT_BASE + 
256kB (0xFFF40000). Saving the environment fails, as U-Boot is unable to 
erase sector 0xFFF40000 which is outside the 16MB flash memory range 
(0xF8000000 - 0xF8FFFFFF).

CFG_FLASH_BASE is used throughout the U-Boot code, so it would not be an easy 
task to replacing it by a variable. Does someone know of a way to either 
detect the flash base address, or read it from a fixed location in flash 
(let's say in the first sector for instance, after the hard reset 
configuration word) ? A possible approach would be to use the hardcoded 
CFG_FLASH_BASE value at startup, and remap the flash at 0xFFFFFFFF - 
flash_size later when the flash size is known. CFG_FLASH_BASE would have to 
be replaced by a variable in several places.

Thanks in advance for all the help you can provide.

Best regards,

Laurent Pinchart