[Mesa-dev] [PATCH 6/7] i965: Reported supported context priorities to EGL/DRI

[Chris Wilson]

Quoting Kenneth Graunke (2017-09-29 20:55:53)
> On Friday, September 29, 2017 3:25:09 AM PDT Chris Wilson wrote:
> > Hook up the RendererQuery for __DRI2_RENDERER_HAS_CONTEXT_PRIORITY to
> > report the available DRM_I915_GEM_CONTEXT_SETPARAM options based on the
> > the default context. The kernel will validate the request to change the
> > property, so we get an accurate reflection of available support (based on
> > kernel version and privilege) and we should only have to do it once
> > during screen setup -- although the SETPARAM should be fast, they are
> > still an ioctl each.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Kenneth Graunke <kenneth at whitecape.org>
> > Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
> > ---
> >  src/mesa/drivers/dri/i965/intel_screen.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
> > index 22d9f19298..112935a580 100644
> > --- a/src/mesa/drivers/dri/i965/intel_screen.c
> > +++ b/src/mesa/drivers/dri/i965/intel_screen.c
> > @@ -1373,6 +1373,19 @@ brw_query_renderer_integer(__DRIscreen *dri_screen,
> >     case __DRI2_RENDERER_HAS_TEXTURE_3D:
> >        value[0] = 1;
> >        return 0;
> > +   case __DRI2_RENDERER_HAS_CONTEXT_PRIORITY:
> > +      value[0] = 0;
> > +      if (brw_hw_context_set_priority(screen->bufmgr,
> > +                                   0, BRW_CONTEXT_HIGH_PRIORITY) == 0)
> > +         value[0] |= __DRI2_RENDERER_HAS_CONTEXT_PRIORITY_HIGH;
> > +      if (brw_hw_context_set_priority(screen->bufmgr,
> > +                                   0, BRW_CONTEXT_LOW_PRIORITY) == 0)
> > +         value[0] |= __DRI2_RENDERER_HAS_CONTEXT_PRIORITY_LOW;
> > +      /* reset to default last, just in case */
> > +      if (brw_hw_context_set_priority(screen->bufmgr,
> > +                                   0, BRW_CONTEXT_MEDIUM_PRIORITY) == 0)
> > +         value[0] |= __DRI2_RENDERER_HAS_CONTEXT_PRIORITY_MEDIUM;
> > +      return 0;
> >     default:
> >        return driQueryRendererIntegerCommon(dri_screen, param, value);
> >     }
> > 
> 
> Interesting, you're setting the priority of the default context (which
> we never use), in order to test whether it works?  Does the kernel
> actually set anything in that case, or does it just ignore it?

It sets it. It's just an integer and applied if the context is ever used
for execbuf. As the kernel does apply the change, we reset to the
default value as the last step. Although it is not stated, we do assume
the query is only performed once at screen creation, so shouldn't be any
concurrency issues..

> If it ignores it, that seems fine.
> 
> Series is:
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
> 
> Typically we wait to pull in new headers until the kernel patches land
> in airlied's drm-next tree.

drm-intel is a non-rebasing tree, once the commit lands there, it is
stable all the way through to linus/master.
-Chris