[PATCH 07/10] drm/amdgpu/ttm: handle tt moves properly.

[Dave Airlie]

On Thu, 24 Sep 2020 at 00:46, Christian König <christian.koenig at amd.com> wrote:
>
> Am 23.09.20 um 05:04 schrieb Dave Airlie:
> > From: Dave Airlie <airlied at redhat.com>
> >
> > The core move code currently handles use_tt moves, for amdgpu
> > this was being handled also in the driver, but not using the same
> > paths.
> >
> > If moving between TT/SYSTEM (all the use_tt paths on amdgpu) use
> > the core move function.
> >
> > Eventually the core will be flipped over to calling the driver.
> >
> > Signed-off-by: Dave Airlie <airlied at redhat.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 12 +++++++-----
> >   1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > index db5f761f37ec..d3bd2fd448be 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > @@ -671,14 +671,16 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
> >               ttm_bo_move_null(bo, new_mem);
> >               return 0;
> >       }
> > -     if ((old_mem->mem_type == TTM_PL_TT &&
> > -          new_mem->mem_type == TTM_PL_SYSTEM) ||
> > -         (old_mem->mem_type == TTM_PL_SYSTEM &&
> > -          new_mem->mem_type == TTM_PL_TT)) {
> > -             /* bind is enough */
> > +     if (old_mem->mem_type == TTM_PL_SYSTEM &&
> > +         new_mem->mem_type == TTM_PL_TT) {
> >               ttm_bo_move_null(bo, new_mem);
>
> I would feel better if we nuke ttm_bo_move_null() and always use
> ttm_bo_move_ttm().

Any reason? The code path in the current move code pretty much
is this.

The current move paths are

if (new_tt && old_tt)
  if old is system
     move null
  else
    move ttm
else
  call driver move.

So I wanted to maintain that order. calling the move ttm will just
make a pointless caching, populate, bind step.

But I'm going to think about it a bit more.

Dave.