[Intel-gfx] [PATCH 18/21] drm/i915/gt: Add timeline "mode"

[Chris Wilson]

Quoting Matthew Brost (2020-12-10 19:28:06)
> On Thu, Dec 10, 2020 at 08:02:37AM +0000, Chris Wilson wrote:
> > diff --git a/drivers/gpu/drm/i915/gt/intel_timeline_types.h b/drivers/gpu/drm/i915/gt/intel_timeline_types.h
> > index f187c5aac11c..32c51425a0c4 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_timeline_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_timeline_types.h
> > @@ -20,6 +20,12 @@ struct i915_syncmap;
> >  struct intel_gt;
> >  struct intel_timeline_hwsp;
> >  
> > +enum intel_timeline_mode {
> > +     INTEL_TIMELINE_ABSOLUTE = 0,
> > +     INTEL_TIMELINE_CONTEXT = BIT(0),
> > +     INTEL_TIMELINE_GLOBAL = BIT(1),
> > +};
> > +
> 
> Not sure I like these names.
> 
> How about:
> INTEL_TIMELINE_ABSOLUTE_GGTT
> INTEL_TIMELINE_RELATIVE_PPGTT
> INTEL_TIMELINE_RELATIVE_GGTT

They are all in the GGTT, including the ppHWSP.

One is relative to the context, the other relative to the engine.

  INTEL_TIMELINE_ABSOLUTE
  INTEL_TIMELINE_RELATIVE_CONTEXT
  INTEL_TIMELINE_RELATIVE_ENGINE

> Also not convinced we need the 'RELATIVE' modes. See my comments in 'Use
> indices for writing into relative'.

It saves extra allocations for when we don't (e.g. gen8, and other
contexts where we know we will never require disposable slots), and
there's a strong incentive to not use absolute addressing with GVT.
-Chris