[Nouveau] RFC: TTM extra bo space

Thomas Hellström thomas at shipmail.org
Sat Nov 7 12:08:59 PST 2009

Jerome Glisse wrote:
> On Thu, 2009-11-05 at 20:04 +0200, Pekka Paalanen wrote:
>> On Wed, 4 Nov 2009 17:42:26 +0000
>> Jakob Bornecrantz <jakob at vmware.com> wrote:
>>> Hi Jerome
>>> On 4 nov 2009, at 15.58, Jerome Glisse wrote:
>>>> Note: For reference my issue is with cursor on old radeon hw,
>>>> cursor must be in the next 128M from the crtc scanout buffer. We
>>>> got issue when someone start to resize their screen at which
>>>> point the scanout buffer can endup after the cursor in vram.
>>>> Other solution would be to add multiple bo adjacent validation
>>>> function to ttm (likely less ttm change).
>>> Can you solve your problem by being able to place the buffer at  
>>> certain location? We had the same need but managed to work around
>>> it with a quick and dirty hack.
>>> Implementing that would mostly be about changing drm_mm.c to
>>> handle placing buffers at certain locations. And in TTM core
>>> being able to evict buffers that are in that place.
>> That sounds like something that could solve an issue in Nouveau
>> with nv04 card family. The following is hearsay, but I try to
>> describe it.
>> Of 32 MB of VRAM, the scanout buffer must reside within the
>> first 16 MB. Any(?) other buffers do not have this limitation
>> e.g. textures. Setting up separate memory spaces for these
>> halves, say, TTM VRAM and TTM PRIV1, would be inconvenient,
>> because buffers could not be laid accross the boundary.
>> Does this make sense?
>> Nouveau people, did I get this right?
Sorry for the late response to this. I'm mostly changing diapers nowadays...

I think this would be excellent. There is a priv member of an mm block 
that can be a bo reference if needed.

I think the semantics should be such that the call would fail with 
-EBUSY if it can not succeed due to pinned buffers in the way, and 
otherwise sleep until it succeeds.


> I am bit busy with bugs right now but i will look into doing
> the actual code soon (one my bug need this).
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