[flashrom] [PATCH] FT2232 error checking

Paul Fox pgf at foxharp.boston.ma.us
Sat Nov 21 20:30:13 CET 2009


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 <pgf at laptop.org>

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 <your at email>
 > 
 > 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 <c-d.hailfinger.devel.2006 at gmx.net>
 > >   
 > 
 > 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
 > 
 > -- 
 > Developer quote of the month: 
 > "We are juggling too many chainsaws and flaming arrows and tigers."

=---------------------
 paul fox, pgf at foxharp.boston.ma.us (arlington, ma, where it's 55.2 degrees)




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