On Tue, Jul 21, 2015 at 03:59:25PM +0200, Maarten Lankhorst wrote:
> Op 21-07-15 om 15:31 schreef Chris Wilson:
> > On Tue, Jul 21, 2015 at 02:33:33PM +0200, Maarten Lankhorst wrote:
> >>>> + if (plane->type == DRM_PLANE_TYPE_PRIMARY && old_obj) {
> >>> Would feel safer is we just asked if the CRTC had pending flips
> >>> irrespective of old_obj. Do you plan on moving the pending flips from
> >>> CRTC to plane? That would seem to be implied here.
> >> This preserves old behavior since page flips can only happen on primary
> >> planes.
> >> Do you want cursor updates to wait on pending primary flips?
> > Cursor updates need to be serialized with primary updates, yes (or else
> > there are some fun scenarios in which you can hang the display engine).
> Ok but right now we don't sync this.. won't blocking on flips for moving the
> mouse in Xorg be bad for performance?
Off the top of my head, we only need to worry about modesets, which
presumedly are serialized between the planes.
> > What I was actually thinking was using plane->state for tracking the
> > flips. Having just reread what I wrote that didn't come across. I would
> > rather see fewer primary_plane special cases and more no-ops on
> > secondary planes. I think you will end up using such infrastructure
> > on the secondary planes eventually.
> I think the current infrastructure will die eventually and perhaps be done
> asynchronously. I just don't know yet what will replace it.
>
> >>>> + /* Big Hammer, we also need to ensure that any pending
> >>>> + * MI_WAIT_FOR_EVENT inside a user batch buffer on the
> >>>> + * current scanout is retired before unpinning the old
> >>>> + * framebuffer. Note that we rely on userspace rendering
> >>>> + * into the buffer attached to the pipe they are waiting
> >>>> + * on. If not, userspace generates a GPU hang with IPEHR
> >>>> + * point to the MI_WAIT_FOR_EVENT.
> >>>> + *
> >>>> + * This should only fail upon a hung GPU, in which case we
> >>>> + * can safely continue.
> >>>> + */
> >>>> + if (!ret && plane->type == DRM_PLANE_TYPE_PRIMARY && old_obj)
> >>>> + ret = i915_gem_object_wait_rendering(old_obj, true);
> >>> Technically I can create a batch with a WAIT_ON_EVENT for a secondary
> >>> plane as well. This path need only be done in a modeset, not for a
> >>> simple plane flip. (But we actually need to serialise with rendering to
> >>> old_obj before regarding the plane flip as complete.) Is there a
> >>> plane-prepare-modeset hook?
> >> The comment didn't explain that, is hiding this behind a
> >> needs_modeset(crtc_state) sufficient here?
> > For the purpose of limiting the wait to when the pipe dimensions may
> > change, yes.
> Is that only needed during full modesets, or when changing PIPESRC too?
The triggers are the display modeline values (whatever HTOTAL/VTOTAL
registers collectively are called), so just full modesets.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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