DRM_ERROR("Forcing to 32M GART size (because of ASIC bug ?)\n");

[Alex Deucher]

On Fri, Jul 16, 2010 at 12:45 AM, Andres Cimmarusti
<andrescimmarusti at yahoo.com> wrote:
>
> In the kernel: drivers/gpu/drm/radeon/rs400.c
>
> You will find this piece of code:
>
>         if (rdev->family == CHIP_RS400 || rdev->family == CHIP_RS480) {
>                 /* FIXME: RS400 & RS480 seems to have issue with GART size
>                  * if 4G of system memory (needs more testing) */
>                 rdev->mc.gtt_size = 32 * 1024 * 1024;
>                 DRM_ERROR("Forcing to 32M GART size (because of ASIC bug ?)\n");
>         }
>
> I don't have 4Gb of system memory (I have 2Gb DDR) so I deleted the whole thing and compiled my kernel fine. Testing it didn't lead me to any problems. My gtt size went from 32Mb to 512Mb. Is this ok? my card is supposed to have 128 Mb of VRAM.
>
> Also if the issue is only when you are above 4Gb of system memory, couldn't there be some sort of if statement that could probe the memory and if it was bigger than 4G then it would force 32mb on gtt memory.?
>
> should I play it safe? I guess I don't really understand what gtt memory is
>

GTT is system memory that is mapped into the video card's address
space so it can be read from or rendered to; it's separate from vram.
I don't recall why we added that quirk, Jerome or Dave may remember,
but I suspect, it should be ok to remove it after this patch:
http://people.freedesktop.org/~agd5f/0001-drm-radeon-kms-fix-gtt-MC-base-alignment-on-rs4xx-rs.patch
is applied.

Alex