Quoting Mika Kuoppala (2017-11-02 15:40:50)
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > In the next few patches, we will have a hard requirement that we emit a
> > context-switch to the perma-pinned i915->kernel_context (so that we can
> > save the HW state using that context-switch). As the first context
> > itself may be classed as a kernel context, we want to be explicit in our
> > comparison. For an extra-layer of finesse, we can check the last
> > unretired context on the engine; as well as the last retired context
> > when idle.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_engine_cs.c | 16 ++++++++++++++--
> > 1 file changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> > index ddbe5c9bf45a..c15e288bed02 100644
> > --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> > @@ -1587,8 +1587,20 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv)
> >
> > bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine)
> > {
> > - return (!engine->last_retired_context ||
> > - i915_gem_context_is_kernel(engine->last_retired_context));
> > + const struct i915_gem_context *kctx = engine->i915->kernel_context;
> > + struct drm_i915_gem_request *rq;
> > +
> > + lockdep_assert_held(&engine->i915->drm.struct_mutex);
> > +
> > + /* An unretired request? */
> > + rq = __i915_gem_active_peek(&engine->timeline->last_request);
> > + if (rq)
> > + return rq->ctx == kctx;
> > +
> > + if (!engine->last_retired_context)
> > + return true;
> > +
> > + return engine->last_retired_context == kctx;
>
>
> Conside that we would have intel_engine_loaded_context(engine)
> {
> rq = __i915_gem_active_peek(&engine->timeline->last_request);
> if (rq)
> return rq->ctx;
>
> if (engine->last_retired_context)
> return engine->last_retired_context;
>
> return NULL;
> }
>
> and then have simple intel_engine_has_kernel_context_loaded()
Could, just needs refinement on the name first. I'll keep one clumsy
name for the moment ;)
> Also further on the patch series we do switch to kernel context
> on init, to grab the hw state. So would it be possible to completely
> get rid of notion that !engine->last_retired_context means kernel
> context? I would rather assert that we have always last retired
> context after init and resume.
Yup, that seems possible.
-Chris
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