Curious experiences with a Radeon on the fritz

[Michael Witten]

On Mon, Sep 26, 2011 at 21:51, Tormod Volden <lists.tormod at gmail.com> wrote:
> On Wed, Sep 21, 2011 at 8:52 PM, Michael Witten wrote:
>> Because my hardware does appear to be malfunctioning due to a corrupt
>> video BIOS, it seems prudent to salvage as much as possible from
>> its output, so that it is possible to figure out which other values
>> need to be hardcoded in case of further corruption.
>>
>> To do this, I did 2 things:
>>
>>  * Export the video BIOS data via debugfs, so that it can be
>>    easily backed up in secondary storage.
>>
>>  * Hack the existing Radeon driver code to log information
>>    about which values are being read from the video BIOS
>>    data and from which offsets these values are being read.
>>
>> I first wrote the following patch to export the video BIOS via debugfs
>> (I wrote a little more than necessary; it should be generally applicable):
>
> Is there any reason to use your debugfs patch instead of reading the
> BIOS the "classic" way?
>
> (as root)
> (use lspci to get the bus id)
> cd /sys/bus/pci/devices/<pci bus id>
> echo 1 > rom
> cat rom > /tmp/vbios.rom
> echo 0 > rom

Most certainly there is a reason: One doesn't yet know it's possible
to read the BIOS the "classic" way. :-D

Of course, in general, the files:

  drivers/gpu/drm/drm_platform.c
  drivers/gpu/drm/drm_usb.c

suggest that it's unwise to rely on PCI. Similarly, things like the function:

  radeon_atrm_get_bios()

suggest that accessing the video BIOS may require the higher-level
access that my patch provides.

Anyway, thanks for the heads-up.