[radeon agp] add blacklist for thinkpad T40p

[Alex Deucher]

On Wed, Dec 2, 2015 at 6:15 AM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 30 November 2015 at 19:47, Alex Deucher <alexdeucher at gmail.com> wrote:
>> On Sat, Nov 28, 2015 at 4:01 PM, Pavel Machek <pavel at ucw.cz> wrote:
>>>
>>> Thinkpad T40p needs agpmode 1.
>>>
>>> Signed-off-by: Pavel Machek <pavel at ucw.cz>
>>
>> Seems odd that this wouldn't have been found earlier given how popular
>> thinkpads are.  Applied.  Thanks,
>>
> Wondering if it wouldn't be better to apply these restrictions within
> the AGP driver. I have a vague recollection that (at least?) some of
> these are chipset limitations/bugs ?

I think it's probably better in the GPU drivers.  AGP was always
problematic.  There are a number of quirks that were necessary for
some users but not others on the same hardware.  Additionally, the
combination of vendors or even driver versions/behaviors were
problematic.  E.g., with UMS, the drivers didn't use much gart since
there was just a single static allocation.  Once we switched to KMS,
lots of new bugs surfaced.  Chipset A plus GPU vendor B worked fined,
but chipset A with GPU vendor C was problematic.

Alex