drm/i915/gt: Track the overall awake/busy time

Since we wake the GT up before executing a request, and go to sleep as
soon as it is retired, the GT wake time not only represents how long the
device is powered up, but also provides a summary, albeit an overestimate,
of the device runtime (i.e. the rc0 time to compare against rc6 time).

v2: s/busy/awake/
v3: software-gt-awake-time and I915_PMU_SOFTWARE_GT_AWAKE_TIME
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215154456.13954-1-chris@chris-wilson.co.uk

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

@@ -11,6 +11,7 @@
 #include "i915_drv.h"
 #include "intel_gt.h"
 #include "intel_gt_clock_utils.h"
+#include "intel_gt_pm.h"
 #include "intel_llc.h"
 #include "intel_rc6.h"
 #include "intel_rps.h"
@@ -558,7 +559,9 @@ static int rps_boost_show(struct seq_file *m, void *data)
 
 	seq_printf(m, "RPS enabled? %s\n", yesno(intel_rps_is_enabled(rps)));
 	seq_printf(m, "RPS active? %s\n", yesno(intel_rps_is_active(rps)));
-	seq_printf(m, "GPU busy? %s\n", yesno(gt->awake));
+	seq_printf(m, "GPU busy? %s, %llums\n",
+		   yesno(gt->awake),
+		   ktime_to_ms(intel_gt_get_awake_time(gt)));
 	seq_printf(m, "Boosts outstanding? %d\n",
 		   atomic_read(&rps->num_waiters));
 	seq_printf(m, "Interactive? %d\n", READ_ONCE(rps->power.interactive));

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

@@ -39,6 +39,28 @@ static void user_forcewake(struct intel_gt *gt, bool suspend)
 	intel_gt_pm_put(gt);
 }
 
+static void runtime_begin(struct intel_gt *gt)
+{
+	local_irq_disable();
+	write_seqcount_begin(&gt->stats.lock);
+	gt->stats.start = ktime_get();
+	gt->stats.active = true;
+	write_seqcount_end(&gt->stats.lock);
+	local_irq_enable();
+}
+
+static void runtime_end(struct intel_gt *gt)
+{
+	local_irq_disable();
+	write_seqcount_begin(&gt->stats.lock);
+	gt->stats.active = false;
+	gt->stats.total =
+		ktime_add(gt->stats.total,
+			  ktime_sub(ktime_get(), gt->stats.start));
+	write_seqcount_end(&gt->stats.lock);
+	local_irq_enable();
+}
+
 static int __gt_unpark(struct intel_wakeref *wf)
 {
 	struct intel_gt *gt = container_of(wf, typeof(*gt), wakeref);
@@ -67,6 +89,7 @@ static int __gt_unpark(struct intel_wakeref *wf)
 	i915_pmu_gt_unparked(i915);
 
 	intel_gt_unpark_requests(gt);
+	runtime_begin(gt);
 
 	return 0;
 }
@@ -79,6 +102,7 @@ static int __gt_park(struct intel_wakeref *wf)
 
 	GT_TRACE(gt, "\n");
 
+	runtime_end(gt);
 	intel_gt_park_requests(gt);
 
 	i915_vma_parked(gt);
@@ -106,6 +130,7 @@ static const struct intel_wakeref_ops wf_ops = {
 void intel_gt_pm_init_early(struct intel_gt *gt)
 {
 	intel_wakeref_init(&gt->wakeref, gt->uncore->rpm, &wf_ops);
+	seqcount_mutex_init(&gt->stats.lock, &gt->wakeref.mutex);
 }
 
 void intel_gt_pm_init(struct intel_gt *gt)
@@ -339,6 +364,30 @@ int intel_gt_runtime_resume(struct intel_gt *gt)
 	return intel_uc_runtime_resume(&gt->uc);
 }
 
+static ktime_t __intel_gt_get_awake_time(const struct intel_gt *gt)
+{
+	ktime_t total = gt->stats.total;
+
+	if (gt->stats.active)
+		total = ktime_add(total,
+				  ktime_sub(ktime_get(), gt->stats.start));
+
+	return total;
+}
+
+ktime_t intel_gt_get_awake_time(const struct intel_gt *gt)
+{
+	unsigned int seq;
+	ktime_t total;
+
+	do {
+		seq = read_seqcount_begin(&gt->stats.lock);
+		total = __intel_gt_get_awake_time(gt);
+	} while (read_seqcount_retry(&gt->stats.lock, seq));
+
+	return total;
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftest_gt_pm.c"
 #endif

drivers/gpu/drm/i915/gt/intel_gt_pm.h

@@ -58,6 +58,8 @@ int intel_gt_resume(struct intel_gt *gt);
 void intel_gt_runtime_suspend(struct intel_gt *gt);
 int intel_gt_runtime_resume(struct intel_gt *gt);
 
+ktime_t intel_gt_get_awake_time(const struct intel_gt *gt);
+
 static inline bool is_mock_gt(const struct intel_gt *gt)
 {
 	return I915_SELFTEST_ONLY(gt->awake == -ENODEV);

drivers/gpu/drm/i915/gt/intel_gt_types.h

@@ -87,6 +87,30 @@ struct intel_gt {
 
 	u32 pm_guc_events;
 
+	struct {
+		bool active;
+
+		/**
+		 * @lock: Lock protecting the below fields.
+		 */
+		seqcount_mutex_t lock;
+
+		/**
+		 * @total: Total time this engine was busy.
+		 *
+		 * Accumulated time not counting the most recent block in cases
+		 * where engine is currently busy (active > 0).
+		 */
+		ktime_t total;
+
+		/**
+		 * @start: Timestamp of the last idle to active transition.
+		 *
+		 * Idle is defined as active == 0, active is active > 0.
+		 */
+		ktime_t start;
+	} stats;
+
 	struct intel_engine_cs *engine[I915_NUM_ENGINES];
 	struct intel_engine_cs *engine_class[MAX_ENGINE_CLASS + 1]
 					    [MAX_ENGINE_INSTANCE + 1];

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1314,9 +1314,10 @@ static int i915_engine_info(struct seq_file *m, void *unused)
 
 	wakeref = intel_runtime_pm_get(&i915->runtime_pm);
 
-	seq_printf(m, "GT awake? %s [%d]\n",
+	seq_printf(m, "GT awake? %s [%d], %llums\n",
 		   yesno(i915->gt.awake),
-		   atomic_read(&i915->gt.wakeref.count));
+		   atomic_read(&i915->gt.wakeref.count),
+		   ktime_to_ms(intel_gt_get_awake_time(&i915->gt)));
 	seq_printf(m, "CS timestamp frequency: %u Hz\n",
 		   RUNTIME_INFO(i915)->cs_timestamp_frequency_hz);
 

drivers/gpu/drm/i915/i915_pmu.c

@@ -509,6 +509,8 @@ config_status(struct drm_i915_private *i915, u64 config)
 		if (!HAS_RC6(i915))
 			return -ENODEV;
 		break;
+	case I915_PMU_SOFTWARE_GT_AWAKE_TIME:
+		break;
 	default:
 		return -ENOENT;
 	}
@@ -616,6 +618,9 @@ static u64 __i915_pmu_event_read(struct perf_event *event)
 		case I915_PMU_RC6_RESIDENCY:
 			val = get_rc6(&i915->gt);
 			break;
+		case I915_PMU_SOFTWARE_GT_AWAKE_TIME:
+			val = ktime_to_ns(intel_gt_get_awake_time(&i915->gt));
+			break;
 		}
 	}
 
@@ -916,6 +921,7 @@ create_event_attributes(struct i915_pmu *pmu)
 		__event(I915_PMU_REQUESTED_FREQUENCY, "requested-frequency", "M"),
 		__event(I915_PMU_INTERRUPTS, "interrupts", NULL),
 		__event(I915_PMU_RC6_RESIDENCY, "rc6-residency", "ns"),
+		__event(I915_PMU_SOFTWARE_GT_AWAKE_TIME, "software-gt-awake-time", "ns"),
 	};
 	static const struct {
 		enum drm_i915_pmu_engine_sample sample;

include/uapi/drm/i915_drm.h

@@ -177,6 +177,7 @@ enum drm_i915_pmu_engine_sample {
 #define I915_PMU_REQUESTED_FREQUENCY	__I915_PMU_OTHER(1)
 #define I915_PMU_INTERRUPTS		__I915_PMU_OTHER(2)
 #define I915_PMU_RC6_RESIDENCY		__I915_PMU_OTHER(3)
+#define I915_PMU_SOFTWARE_GT_AWAKE_TIME	__I915_PMU_OTHER(4)
 
 #define I915_PMU_LAST /* Deprecated - do not use */ I915_PMU_RC6_RESIDENCY