Re: [flashrom] [PATCH] FT2232 error checking

[Paul Fox]

hi carl-daniel --

sorry for the delay -- things have been pretty busy recently. 
that patch certainly looks correct.  i haven't been able to try
it, but i'll probably be doing some reflashing soon...

Acked-by: Paul Fox

paul

carl-daniel wrote:
> Hi Paul, hi Richard,
>
> I remember that one of you mentioned occassional verify failures with
> flashrom and the FT2232 code.
> The good news is that we recently got a report from another user (Jeremy
> Buseman) with whom we could track down some of the issues to timing and
> to deficiencies in the software/hardware stack. Running flashrom in
> non-verbose mode and with a limit of 36 bytes per SPI command (1 opcode,
> 3 address, 32 data) gave him 100% reliable results.
> I also have a patch pending which allows a specialized test pattern to
> be burned, and the results were surprising: Sometimes, the last two
> bytes of a 64-byte block are simply missing, then the next 64-byte block
> is moved two bytes in the direction of lower addresses, and so on. For
> page (256 byte) reads, this could result in up to 8 bytes at the end
> being undefined because some or all 64-byte subpages had been trimmed.
> Besides that, verbose mode seems to have thrown off the timing enough to
> cause read/write errors as well. In theory, that should not happen (and
> libftdi/libusb should ensure consistent behaviour), but reality seems a
> bit disillusioning.
>
> If you could review the patch below which adds some error checking to
> give at least some indications on where the problems may lie, I'd
> appreciate it. It is entirely possible that you won't get additional
> warnings from the patch, but I'd like to run it past you because you
> seem to be responsible for the largest FT2232 flashrom deployment. If
> you think the patch is OK, please respond with
> > Acked-by: Your Name
>
> On 10.11.2009 04:07, Carl-Daniel Hailfinger wrote:
> > Pretty much everybody who used the FT2232 SPI driver in flashrom had
> > problems with incorrect reads from time to time.
> > One reason was that the hardware is pretty timing sensitive even for reads.
> >
> > The other reason was that the code silently ignored errors. This patch
> > doesn't add any error recovery, but it will emit error messages if
> > FT2232 communication goes wrong. That allows us to track down errors
> > without investing hours in driver debugging.
> >
> > Jeremy, I'd be very interested in the results of an unmodified flashrom
> > with only this patch applied (read is sufficient). In theory, you should
> > either get a working read or loads of error messages about
> > send_buf/read_buf. If you get no error messages and the image read is
> > still wrong, libftdi doesn't tell us about the problem. Oh, and please
> > try in verbose and normal mode. Maybe there's a difference.
> >
> > Signed-off-by: Carl-Daniel Hailfinger
>
> In case you're not subscribed to the flashrom mailing list, you can
> download the patch here:
> http://patchwork.coreboot.org/patch/549/raw/
>
> Regards,
> Carl-Daniel

=---------------------
 paul fox, [e-mail] (arlington, ma, where it's 55.2 degrees)