[U-Boot] CFI: flash_write_cfiword() slow

[Jens Gehrlein <sew_s@tqs.de>]

Hi list,

having a look at function 
drivers/mtd/cfi_flash.c::flash_write_cfiword(), I found that 
find_sector() is called twice when having AMD standard, extended or 
legacy device. The first time, when writing the command. The second 
time, when calling flash_full_status_check().

Maybe this is the reason, why this programming mode is so slow.
find_sector() loops through the sector table from the last sector to
the current sector. And the more sectors the device has, the slower
the algorithm becomes. And this process for every sector to be 
programmed. And yes, there are still devices around without (standard) 
write buffer, e.g. the Samsung K8P2815UQB.

Before spending time to create a patch, I would like to read your 
opinion about this proposal/question:
Would it be sufficient to just add a flag, that indicates, that the 
sector number has already been calculated for AMD flashes or would it be 
better to pass parameters to flash_full_status_check() dependent on the 
command set?
Other proposals?
Do you see any unwanted side effects?

-- 
Kind regards,
Jens