[PATCH 2/2] now

[Chris Wilson]

---
 drivers/gpu/drm/i915/gt/intel_engine.h       | 10 +++++++++-
 drivers/gpu/drm/i915/gt/intel_engine_cs.c    | 12 +++++++-----
 drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 17 +++++++----------
 3 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 791897f8d847..0f2b8613286b 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -334,7 +334,15 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 		       struct drm_printer *m,
 		       const char *header, ...);
 
-ktime_t intel_engine_get_busy_time(struct intel_engine_cs *engine);
+ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine,
+				     ktime_t *now);
+
+static inline ktime_t intel_engine_get_busy_time(struct intel_engine_cs *engine)
+{
+	ktime_t dummy;
+
+	return __intel_engine_get_busy_time(engine, &dummy);
+}
 
 struct i915_request *
 intel_engine_find_active_request(struct intel_engine_cs *engine);
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 045179c65c44..916018909a9e 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1595,7 +1595,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 	intel_engine_print_breadcrumbs(engine, m);
 }
 
-static ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine)
+static ktime_t __get_busy_time(struct intel_engine_cs *engine, ktime_t *now)
 {
 	ktime_t total = engine->stats.total;
 
@@ -1603,9 +1603,9 @@ static ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine)
 	 * If the engine is executing something at the moment
 	 * add it to the total.
 	 */
+	*now = ktime_get();
 	if (atomic_read(&engine->stats.active))
-		total = ktime_add(total,
-				  ktime_sub(ktime_get(), engine->stats.start));
+		total = ktime_add(total, ktime_sub(*now, engine->stats.start));
 
 	return total;
 }
@@ -1613,17 +1613,19 @@ static ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine)
 /**
  * intel_engine_get_busy_time() - Return current accumulated engine busyness
  * @engine: engine to report on
+ * @now: monotonic timestamp of sampling
  *
  * Returns accumulated time @engine was busy since engine stats were enabled.
  */
-ktime_t intel_engine_get_busy_time(struct intel_engine_cs *engine)
+ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine,
+				     ktime_t *now)
 {
 	unsigned int seq;
 	ktime_t total;
 
 	do {
 		seq = read_seqbegin(&engine->stats.lock);
-		total = __intel_engine_get_busy_time(engine);
+		total = __get_busy_time(engine, now);
 	} while (read_seqretry(&engine->stats.lock, seq));
 
 	return total;
diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
index dd54dcb5cca2..9ad9c8b55e4a 100644
--- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
@@ -29,8 +29,8 @@ static int live_engine_busy_stats(void *arg)
 	GEM_BUG_ON(intel_gt_pm_is_awake(gt));
 	for_each_engine(engine, gt, id) {
 		struct i915_request *rq;
-		ktime_t de;
-		u64 dt;
+		ktime_t de, dt;
+		ktime_t t[2];
 
 		if (!intel_engine_supports_stats(engine))
 			continue;
@@ -47,11 +47,9 @@ static int live_engine_busy_stats(void *arg)
 
 		ENGINE_TRACE(engine, "measuring idle time\n");
 		preempt_disable();
-		dt = ktime_to_ns(ktime_get());
-		de = intel_engine_get_busy_time(engine);
+		de = __intel_engine_get_busy_time(engine, &t[0]);
 		udelay(100);
-		de = ktime_sub(intel_engine_get_busy_time(engine), de);
-		dt = ktime_to_ns(ktime_get()) - dt;
+		de = ktime_sub(__intel_engine_get_busy_time(engine, &t[1]), de);
 		preempt_enable();
 		if (de < 0 || de > 10) {
 			pr_err("%s: reported %lldns [%d%%] busyness while sleeping [for %lldns]\n",
@@ -80,12 +78,11 @@ static int live_engine_busy_stats(void *arg)
 
 		ENGINE_TRACE(engine, "measuring busy time\n");
 		preempt_disable();
-		dt = ktime_to_ns(ktime_get());
-		de = intel_engine_get_busy_time(engine);
+		de = __intel_engine_get_busy_time(engine, &t[0]);
 		udelay(100);
-		de = ktime_sub(intel_engine_get_busy_time(engine), de);
-		dt = ktime_to_ns(ktime_get()) - dt;
+		de = ktime_sub(__intel_engine_get_busy_time(engine, &t[1]), de);
 		preempt_enable();
+		dt = ktime_sub(t[1], t[0]);
 		if (100 * de < 95 * dt || 95 * de > 100 * dt) {
 			pr_err("%s: reported %lldns [%d%%] busyness while spinning [for %lldns]\n",
 			       engine->name,
-- 
2.20.1