Hi Michael,
On Friday 02 November 2007, Michael Schwingen wrote:
I am currently porting u-boot to multiple IXP425-based boards that have accumulated here over the time. One of them has a slight problem, because it uses a combination of two flash roms:
- one 8-bit SST 39VF020 boot flash on a 8-bit chip select as boot flash
- one 16-bit Intel 64MBit flash on a 16-bit chip select.
The intel flash is CFI, while the SST flash is not. I want to use both flash roms, and I want to use as much of the existing flash code as possible. It seems that when using the CFI code, there is no easy way to add a non-CFI flash - right?
Correct. This is currently known limitation.
What would be the best way to use both flash roms? I have come up with:
(1) provide a hook in cfi_flash.c to insert hardcoded values into the flash_info structure for the non-CFI flash rom. Due to differences between CFI-AMD and non-CFI AMD flash command cycles, I need to add a new commandset (eg. CFI_CMDSET_AMD_LEGACY) plus a bit of handler code.
(2) rename all external-visible functions in flash_cfi.c and add wrapper functions that call either the CFI code or my own code for the non-CFI flash. This has the disadvantage that I need to duplicate code that is already present in cfi_flash.c, but is not exported. I have ssen this done on one chip vendor's u-boot port, and it does not really look nice.
(3) extend the code in cfi_flash.c so that external functions can be added via function pointers for non-CFI flashs. Same disadvantage as (2).
I have implemented solution (1) now, and it seems to work quite well, with minimal code needed in the board-setup file, but maybe there are better ways to do this - comments?
I remember a discussion we had a while ago, about supporting non-CFI chips in a common driver, but I can't find the mails right now. IIRC, the idea was to add something close to the Linux JEDEC probe (drivers/mtd/chips/jedec_probe.c) for this.
I suggest that you post your current version for review. This sounds like a start in the correct direction.
Thanks.
Best regards, Stefan
===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: office@denx.de =====================================================================