[Intel-gfx] [PATCH] drm/i915: fix plane/cursor handling when runtime suspended

[Chris Wilson]

On Tue, Aug 12, 2014 at 10:19:20PM +0200, Daniel Vetter wrote:
> On Tue, Aug 12, 2014 at 9:33 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
> > 2014-08-12 16:28 GMT-03:00 Chris Wilson <chris at chris-wilson.co.uk>:
> >> On Tue, Aug 12, 2014 at 04:12:38PM -0300, Paulo Zanoni wrote:
> >>> But we just get/put RPM around this function, not for the whole time
> >>> while the object is pinned.
> >>
> >> Ah misread, saw pin->get, unpin->put and assumed the symmetry. But why
> >> unpin then? It doesn't touch any hardware registers.
> >
> > Only because Daniel asked it on a conversation we had on IRC, and I
> > automatically assumed the patch would be rejected if I didn't include
> > it :)
> >
> > Since both you and VIlle pointed that out, I should probably submit
> > yet another version, without the unpin part, and let Daniel choose
> > which one to merge...
> 
> Hm, I've indeed forgotten about the lazy unbinding. But that poses the
> question about the final bo unref. For example:
> 1) create bo, gtt mmap it to force it into existence (and into the global gtt)
> 2) unmap binding
> 3) wait for rpm entry
> 4) unref bo ... causing pte writes for the global gtt unbinding while
> runtime suspended or not?
> 
> boom or not boom?
> 
> Maybe the bug is simply in a different function ;-)

Yes. If you get serious about it, you will want to move the lazy stuff
into its own workqueue to be run the next time the device is awake.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre