[PATCH] drm/ttm: do not try to preserve caching state

[Jerome Glisse]

On Wed, Nov 28, 2012 at 5:18 PM, Thomas Hellstrom <thomas at shipmail.org> wrote:
> On 11/28/2012 09:09 PM, Jerome Glisse wrote:
>>
>> On Wed, Nov 28, 2012 at 10:05 AM,  <j.glisse at gmail.com> wrote:
>>>
>>> From: Jerome Glisse <jglisse at redhat.com>
>>>
>>> It make no sense to preserve caching state especialy when
>>> moving from vram to system. It burden the page allocator to
>>> match the vram caching (often WC) which just burn CPU cycle
>>> for no good reasons.
>
>
> Nack.
> This is a driver problem.
>
> What happens with this patch if you evict write-combined TT memory to
> system?
> That's why we want to preserve caching state in the first place.
>
> If you need a different behavior, you can fine-tune in driver::evict_flags,
> or in the
> radeon-case in radeon_move_ram_vram / radeon_move_vram_ram.

No you can't. Because cur placement of vram will be wc, and thus it
will want to preserve it for gtt. Only way to force it is to declare
vram as cached too.

Cheers,
Jerome