[Mesa-dev] [PATCH 05/10] i965: Use Global GTT for Sandybridge post-sync non-zero workaround.

[Eric Anholt]

Eric Anholt <eric at anholt.net> writes:

> Kenneth Graunke <kenneth at whitecape.org> writes:
>
>> The kernel doesn't even set up the aliasing PPGTT on Sandybridge, so any
>> writes marked as PPGTT will likely just get dropped on the floor.
>
> The hardware bug is that writes not marked as GTT are still looked up in
> the GTT anyway.
>
> The kernel does set up the PPGTT, which is how we found we needed to put
> in the kernel workaround based on DOMAIN_INSTRUCTION (of binding the
> target buffer to the gtt as well as the ppgtt, since the writes landed
> in the wrong place)
>
> I don't think this patch will change anything, but it seems reasonable
> if the commit message is updated.

Actually, thinking about it more, I'd rather not explicitly use global
GTT, unless the function is also renamed to
gen6_emit_post_sync_nonzero_workaround, since now this function on
non-gen6 would reference GTT memory in its instruction, but the kernel
wouldn't put anything in the GTT.

(I'd rather just leave the workaround as is, myself).
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 835 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20140110/b7fe2c33/attachment.pgp>