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

[John Paul Adrian Glaubitz]

On 5/11/20 10:12 PM, Christian König wrote:
> I unfortunately only have an x86 Mac to test this on, but as far as I know the Radeon
> AGP support for PowerPC is disabled for years already because it didn't worked reliable.

I have a current Debian unstable running on an iBook G4 with Radeon graphics enabled
on a current kernel and graphics stack and it runs fine. Not sure though whether
it currently employs all AGP features, but I would like to be able to continue
using it and so are the users on the debian-powerpc mailing list.

>>> So the idea here is to just go ahead and remove the support from Radeon and Nouveau and
>>> then drop the necessary code from TTM.
>>> For Radeon this means that we just switch over to the driver specific page tables and
>>> everything should more or less continue to work.
>>>
>>> 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].
> 
> Please note that at least the Mac I was able to test with Radeon hardware just continuous
> to work. But it is certainly possible that some pre r3xx generation hardware will break with this.
> 
> We just stop using this bogus idea of trying to use uncached system memory as "extension" of the
> on board video memory and instead switch to the reliable device internal GART.

Well, the title "Remove AGP support" in the subject implied something else to me which
is why I wrote this mail. If this just applies to the mechanism to allow system memory
to be used as graphics memory, the results may be different.

> Maybe we should just deprecate the configuration option first?

Would this change imply the removal of CONFIG_AGP_*? If yes, I assume that would
kill CONFIG_AGP_UNINORTH which we have enabled on our PowerPC kernels for powerpc
and ppc64.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
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