[Intel-gfx] [PATCH] drm/i915: Track pinned vma in intel_plane_state

[Chris Wilson]

On Wed, Jan 04, 2017 at 06:06:42PM +0200, Ville Syrjälä wrote:
> On Wed, Jan 04, 2017 at 04:00:49PM +0000, Chris Wilson wrote:
> > If we are restoring the same plane_state, the old_plane_state will not
> > be unpinned until after the swap. So prepare_fb will return the
> > duplicate VMA with incremented pin_count.
> 
> During suspend we throw away the old state, and resume will read in
> the state from the hardware. So when we do the swap we won't have the
> original old state in place anymore.

But in this case, we should have a plane_config from HW readout that has
a recovered VMA? I presume the same takeover code is run after resume as
on init...

On the other hand, if the plane_state was removed from the hardware, its
VMA would be unpinned and we would be free to rebind it in a new location.
Provided the obj itself wasn't freed, the VMA will be kept. However, we
still risk a potential error on remapping (if the vma was unbound during
suspend). That's not a huge risk though, and does require the VMA to be
actually unbound on suspend.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre