[Intel-gfx] [PATCH 1/1] Let userspace know if they can trust timeslicing by including it as part of the I915_PARAM_HAS_SCHEDULER::I915_SCHEDULER_CAP_TIMESLICING

[Daniel Vetter]

On Tue, May 25, 2021 at 03:19:47PM +0100, Tvrtko Ursulin wrote:
> 
> + dri-devel as per process
> 
> On 25/05/2021 14:55, Tejas Upadhyay wrote:
> > v2: Only declare timeslicing if we can safely preempt userspace.
> 
> Commit message got butchered up somehow so you'll need to fix that at some
> point.
> 
> Regards,
> 
> Tvrtko
> 
> > Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_engine_user.c | 1 +
> >   include/uapi/drm/i915_drm.h                 | 1 +
> >   2 files changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > index 3cca7ea2d6ea..12d165566ed2 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > @@ -98,6 +98,7 @@ static void set_scheduler_caps(struct drm_i915_private *i915)
> >   		MAP(HAS_PREEMPTION, PREEMPTION),
> >   		MAP(HAS_SEMAPHORES, SEMAPHORES),
> >   		MAP(SUPPORTS_STATS, ENGINE_BUSY_STATS),
> > +		MAP(TIMESLICE_BIT, TIMESLICING),
> >   #undef MAP
> >   	};
> >   	struct intel_engine_cs *engine;
> > diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> > index c2c7759b7d2e..af2212d6113c 100644
> > --- a/include/uapi/drm/i915_drm.h
> > +++ b/include/uapi/drm/i915_drm.h
> > @@ -572,6 +572,7 @@ typedef struct drm_i915_irq_wait {
> >   #define   I915_SCHEDULER_CAP_PREEMPTION	(1ul << 2)
> >   #define   I915_SCHEDULER_CAP_SEMAPHORES	(1ul << 3)
> >   #define   I915_SCHEDULER_CAP_ENGINE_BUSY_STATS	(1ul << 4)
> > +#define   I915_SCHEDULER_CAP_TIMESLICING	(1ul << 5)

Since this is uapi I think we should at least have some nice kerneldoc
that explains what exactly this is, what for (link to userspace) and all
that. Ideally also minimally filing in the gaps in our uapi docs for stuff
this references.
-Daniel

> >   #define I915_PARAM_HUC_STATUS		 42
> > 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch