[Intel-gfx] [PATCH v2] drm/i915/gt: Declare when we enabled timeslicing

[Chris Wilson]

Let userspace know if they can trust timeslicing by including it as part
of the I915_PARAM_HAS_SCHEDULER::I915_SCHEDULER_CAP_TIMESLICING

v2: Only declare timeslicing if we can safely preempt userspace.

Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Kenneth Graunke <kenneth at whitecape.org>
---
 drivers/gpu/drm/i915/gt/intel_engine.h      | 3 ++-
 drivers/gpu/drm/i915/gt/intel_engine_user.c | 5 +++++
 include/uapi/drm/i915_drm.h                 | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 29c8c03c5caa..a32dc82a90d4 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -326,7 +326,8 @@ intel_engine_has_timeslices(const struct intel_engine_cs *engine)
 	if (!IS_ACTIVE(CONFIG_DRM_I915_TIMESLICE_DURATION))
 		return false;
 
-	return intel_engine_has_semaphores(engine);
+	return (intel_engine_has_semaphores(engine) &&
+		intel_engine_has_preemption(engine));
 }
 
 #endif /* _INTEL_RINGBUFFER_H_ */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c
index 848decee9066..b84fdd722781 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_user.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c
@@ -121,6 +121,11 @@ static void set_scheduler_caps(struct drm_i915_private *i915)
 			else
 				disabled |= BIT(map[i].sched);
 		}
+
+		if (intel_engine_has_timeslices(engine))
+			enabled |= I915_SCHEDULER_CAP_TIMESLICING;
+		else
+			disabled |= I915_SCHEDULER_CAP_TIMESLICING;
 	}
 
 	i915->caps.scheduler = enabled & ~disabled;
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 829c0a48577f..f4d521f51258 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -523,6 +523,7 @@ 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)
 
 #define I915_PARAM_HUC_STATUS		 42
 
-- 
2.25.0