Am 11.05.20 um 21:55 schrieb John Paul Adrian Glaubitz:
Hi Christian!
Well let's face it AGP is a total headache to maintain and dead for at least
10+ years.
We have a lot of x86 specific stuff in the architecture independent graphics
memory management
to get the caching right, abusing the DMA API on multiple occasions, need to
distinct between
AGP and driver specific page tables etc etc...
AGP isn't exclusively used on x86 but there are also a lot of PowerPC desktop
machines (Apple
PowerMac, Pegasos etc) that employ AGP graphics.
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.
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.
Maybe we should just deprecate the configuration option first?
I have also CC'ed the debian-powerpc mailing list so that other users can voice
their
opinion.
Thanks for that.
Regards,
Christian.
Thanks,
Adrian
[1] https://cdimage.debian.org/cdimage/ports/2020-04-19/
