drm/i915: Show support for accurate sw PMU busyness tracking

Expose whether or not we support the PMU software tracking in our
scheduler capabilities, so userspace can query at runtime.

v2: Use I915_SCHEDULER_CAP_ENGINE_BUSY_STATS for a less ambiguous
capability name.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190703143702.11339-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -688,9 +688,10 @@ void intel_engines_set_scheduler_caps(struct drm_i915_private *i915)
 		u8 engine;
 		u8 sched;
 	} map[] = {
-#define MAP(x, y) { ilog2(I915_ENGINE_HAS_##x), ilog2(I915_SCHEDULER_CAP_##y) }
-		MAP(PREEMPTION, PREEMPTION),
-		MAP(SEMAPHORES, SEMAPHORES),
+#define MAP(x, y) { ilog2(I915_ENGINE_##x), ilog2(I915_SCHEDULER_CAP_##y) }
+		MAP(HAS_PREEMPTION, PREEMPTION),
+		MAP(HAS_SEMAPHORES, SEMAPHORES),
+		MAP(SUPPORTS_STATS, ENGINE_BUSY_STATS),
 #undef MAP
 	};
 	struct intel_engine_cs *engine;

drivers/gpu/drm/i915/i915_pmu.c

@@ -102,10 +102,8 @@ static bool pmu_needs_timer(struct drm_i915_private *i915, bool gpu_active)
 	/*
 	 * Also there is software busyness tracking available we do not
 	 * need the timer for I915_SAMPLE_BUSY counter.
-	 *
-	 * Use RCS as proxy for all engines.
 	 */
-	else if (intel_engine_supports_stats(i915->engine[RCS0]))
+	else if (i915->caps.scheduler & I915_SCHEDULER_CAP_ENGINE_BUSY_STATS)
 		enable &= ~BIT(I915_SAMPLE_BUSY);
 
 	/*

include/uapi/drm/i915_drm.h

@@ -521,6 +521,7 @@ typedef struct drm_i915_irq_wait {
 #define   I915_SCHEDULER_CAP_PRIORITY	(1ul << 1)
 #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_PARAM_HUC_STATUS		 42