[flashrom] Debugging FT4232H

David Hendricks dhendrix at google.com
Thu Apr 28 23:51:54 CEST 2011


On Mon, Apr 25, 2011 at 5:53 PM, Carl-Daniel Hailfinger <
c-d.hailfinger.devel.2006 at gmx.net> wrote:

> Hi,
>
> Am 26.04.2011 00:43 schrieb David Hendricks:
>
>  I'm using Flashrom with an FTDI FT4232H to read a 1MB SPI ROM (w25q80),
>> but
>> am encountering difficulties. I believe we may be missing some steps in
>> ft2232_spi_init(), however I don't have much experience with libftdi or
>> usb
>> debugging so I hope someone on the list does :-)
>>
>> When the programmer is plugged into a "full-speed" USB port slow, things
>> seem to work well. However, when plugged into a "high-speed" port, bytes
>> simply disappear. There does not seem to be a pattern with regard to where
>> the problems start. Sometimes it will fail very early and Flashrom will
>> not
>> be able to detect the chip. Sometimes we'll get lucky and we can read the
>> full chip. It can fail anywhere in between.
>>
>> The only pattern I've seen is that usb bulk reads return less than the
>> requested number of bytes before it fails entirely. For example, if we
>> request 256 bytes, then it might return 256-N data bytes. libftdi will
>> request the remaining bytes, and libusb will provide the remaining N data
>> bytes. On the next 256-byte request, libusb will not return any data bytes
>> (only the 2-byte USB header).
>>
>>
>
> This is a known problem which may happen with older (>6 months) libftdi
> and/or older kernels (>6 months) and/or older libusb. The libftdi mailing
> list probably has more information. If you can reproduce the issue with a
> recent kernel (2.6.36 or newer) and recent libusb and libftdi from git,
> please tell the libftdi mailing list.
> IIRC some flashrom patch (sent in the last 6 months or so) tried to make
> sure that such issues are worked around in flashrom by requiring recent
> libftdi and by setting a parameter which reduces the likelihood of that
> event. Sorry, I don't have more details handy right now.


Quick follow up -- I got a chance to try flashrom out with the FT4232H out
on machine with a 2.6.38 kernel and it worked great, EHCI high speed and all
:-)

Thanks for the pointer!

-- 
David Hendricks (dhendrix)
Systems Software Engineer, Google Inc.
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