[flashrom] Can't probe AT26DF321 on OptiPlex 755

[Stefan Tauner]

On Thu, 13 Aug 2015 16:17:20 -0400
"Patrick 'P. J.' McDermott" <pj at baldr1.pehjota.net> wrote:

> 
> Although I don't have schematics, I see resistors on the board on the
> CS#, SO, WP#, SCK, NC/HOLD#, and VCC lines, indicating that the board is
> likely designed for ISP.

Not necessarily. Could be simple pull-ups (and a current limiter on
VCC)...?

> damo22 looked at the datasheet [1] (the AT25 datasheet [2] is almost
> identical) and suggested that maybe the chip is in Deep Power-Down mode,
> which would explain why it's not responding to commands from flashrom on
> an external linux_spi programmer.
> 
> Is it possible that the AT26DF321 on this board is always put in Deep
> Power-Down mode by the ICH9 (Intel 82801IO) but the AT26DF321 on the
> other board I successfully tried (with an Intel 82801IEM ICH9M-E) is
> normally in standby?  Has anyone else ever encountered an SPI flash chip
> in Deep Power-Down mode?
> 
> I looked through the source code to see if flashrom sends or could send
> a Resume from Deep Power-Down command.  The command is a 0xAB opcode
> while CS# is asserted, followed by a deassertion of CS# and a delay of
> up to 3 µs.  flashrom doesn't send this command, but all of that seems
> easily doable except for the CS# deassertion.  Linux's
> Documentation/spi/spidev file says that the SPI_IOC_MESSAGE(N) request
> does not deselect the chip.

flashrom DOES send 0xAB (RES) as it is one of the opcodes that can be
used to identify flash chips (look for probe_spi_res1 in your log).

> Any recommendations on how to proceed?

Unfortunately, I don't have another explanation other than that the
board simply does not work with ISP. Have you tried measuring actual
voltages on the board while flashrom is running or even using a logic
analyzer?

-- 
Kind regards/Mit freundlichen Grüßen, Stefan Tauner