[RFC] Remove AGP support from Radeon/Nouveau/TTM

[Christian König]

Am 11.05.20 um 22:46 schrieb Alex Deucher:
> On Mon, May 11, 2020 at 4:41 PM John Paul Adrian Glaubitz
> <glaubitz at physik.fu-berlin.de> wrote:
>> On 5/11/20 10:05 PM, Alex Deucher wrote:
>>>>> For Nouveau I'm not 100% sure, but from the code it of hand looks like we can do it similar to Radeon.
>>>>>
>>>>> Please comment what you think about this.
>>>> I would be against such a move as AGP graphics is still used by people running the powerpc
>>>> and ppc64 Debian ports on their vintage hardware [1].
>>>>
>>>> I have also CC'ed the debian-powerpc mailing list so that other users can voice their
>>>> opinion.
>>> Note there is no loss of functionality here, at least on radeon
>>> hardware.  It just comes down to which MMU gets used for access to
>>> system memory, the AGP MMU on the chipset or the MMU built into the
>>> GPU.  On powerpc hardware, AGP has been particularly unstable, and
>>> IIRC, AGP has been disabled by default on radeon on powerpc for a
>>> while.
>> Do you have a code reference at hand for this bit of information (AGP
>> being disabled on Macs)?
> It was disabled 2 years ago:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=037d1a66ae640ca2723f47c0115ffa9e603699b3

To be honest from the hacks we have in there to get this working I'm 
even surprised that this ever worked at all on PowerPC.

Going to extend this patch for now and add a config option to not 
compile in AGP GART support for TTM any more instead of removing it.

Christian.

>
> Alex
>
>> Thanks,
>> Adrian
>>
>> --
>>   .''`.  John Paul Adrian Glaubitz
>> : :' :  Debian Developer - glaubitz at debian.org
>> `. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
>>    `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913