[flashrom] Debugging FT4232H

[Carl-Daniel Hailfinger]

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.

Regards,
Carl-Daniel

-- 
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