[flashrom] flashrom v0.9.9-r1955 FAILS ON sst25lf080(a) with ch341a_spi

[Nico Huber]

Hi Boyce, Josh,

On 13.06.2017 16:24, Boyce Humphries via flashrom wrote:
> Hello Josh
>
> I dove into the code yesterday and here is what I found.  When the bits
> BP0 and BP1 in the status register need to be cleared the function
> spi_disable_blockprotect(flash) is called.  To clear these bits (for the
> sst25lf080a ROM chip) the commands EWSR and WRSR need to be sent to the
> chip.  In the function spi_write_status_register(...) the function
> spi_write_status_register_flag(...) is call to send the commands WREN
> and WRSR.  The expectation seems to be that if this function fails to
> clear BP0 and BP1 bits it will return a no-zerero value and then
> spi_write_status_register_flag(...)  will be call again to send the
> commands EWSR and WRSR.  But spi_write_status_register_flag(...) returns
> a zero value for the first case so the second calll is never made.  The
> EWSR and WRSR commands are never sent and the chip remains in protected
> mode.

this looks very odd indeed, but it can be explained: There is at least
one programmer supported by flashrom (Intel southbridges) that can
limit the opcodes. If a chip would support both sequences, the first
call could indeed fail while the second could work. I'm not 100% sure
but this could be why this code is written as is, and why there is a
FEATURE_WRSR_EITHER (see below).

> 
> To correct the code the commands EWSR and WRSR must be sent to the
> sst25lf080a.  How this should be done so that the code works for other
> chips I leave to the people at flashrom.

Very simple set FEATURE_WRSR_EWSR instead of FEATURE_WRSR_EITHER in
flashchips.c for SST25LF080A. Maybe there really is a SST25LF080 that
supports (WREN, WRSR), but I couldn't find a clue and doubt it.

Please try that and report back. Preferably with a log taken with
`flashrom -o logfile.txt ...` if it works.

> 
> Still a mystery is how the code works for the sst25lf040a chip and not
> the sst25lf080a chip.

The former has FEATURE_WRSR_EWSR set correctly.

Nico