Switch reference counting to GEM instead of TTM

[Danilo Krummrich]

Hi Christian,

On 7/16/24 2:35 PM, Christian König wrote:
> Hello everyone,
> 
> to make use of drm_exec it is necessary to have TTM drivers actually use
> the GEM reference count instead of the TTM one.
> 
> This patch set is a start to do that. It switches all uses of
> ttm_bo_get/put to the GEM counterpart and then makes ttm_bo_get private
> to TTM.

That makes a lot of sense.

But I think for at least some drivers it requires a bit more than just
replacing ttm_bo_{get, put} with drm_gem_object_{get, put}.

I gave this a quick shot on Nouveau, and as is, it creates a refcount
underflow for the GEM object's reference count.

At a first glance this seems to happen because some of the previous 
ttm_bo_put() calls intend to compensate for the initial refcount of a 
ttm_buffer_object.

I will have a closer look later on.

- Danilo

> 
> Netx step is to completely remove the TTM refcounting.
> 
> Please review and/or comment.
> 
> Cheers,
> Christian.
> 
>