[PATCH v1] drm/i915/selftests: Improve RC6 power measurement and error handling

[Sk Anirban <sk.anirban@xxxxxxxxx>]

Improve RC6 power measurement and error handling. Add detailed error
messages, and introduce a threshold check for RC6 residency.

Signed-off-by: Sk Anirban <sk.anirban@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/selftest_rc6.c | 61 +++++++++++++++++---------
 1 file changed, 40 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_rc6.c b/drivers/gpu/drm/i915/gt/selftest_rc6.c
index 908483ab0bc8..30bc2ff040ce 100644
--- a/drivers/gpu/drm/i915/gt/selftest_rc6.c
+++ b/drivers/gpu/drm/i915/gt/selftest_rc6.c
@@ -33,15 +33,20 @@ int live_rc6_manual(void *arg)
 {
 	struct intel_gt *gt = arg;
 	struct intel_rc6 *rc6 = &gt->rc6;
-	u64 rc0_power, rc6_power;
+	struct intel_rps *rps = &gt->rps;
 	intel_wakeref_t wakeref;
+	u64 sleep_time = 1000;
+	u32 rc0_freq = 0;
+	u32 rc6_freq = 0;
+	u64 rc0_power[3];
+	u64 rc6_power[3];
 	bool has_power;
+	u64 threshold;
 	ktime_t dt;
 	u64 res[2];
 	int err = 0;
-	u32 rc0_freq = 0;
-	u32 rc6_freq = 0;
-	struct intel_rps *rps = &gt->rps;
+	u64 diff;
+
 
 	/*
 	 * Our claim is that we can "encourage" the GPU to enter rc6 at will.
@@ -65,9 +70,9 @@ int live_rc6_manual(void *arg)
 	res[0] = rc6_residency(rc6);
 
 	dt = ktime_get();
-	rc0_power = librapl_energy_uJ();
-	msleep(1000);
-	rc0_power = librapl_energy_uJ() - rc0_power;
+	rc0_power[0] = librapl_energy_uJ();
+	msleep(sleep_time);
+	rc0_power[1] = librapl_energy_uJ() - rc0_power[0];
 	dt = ktime_sub(ktime_get(), dt);
 	res[1] = rc6_residency(rc6);
 	rc0_freq = intel_rps_read_actual_frequency_fw(rps);
@@ -79,11 +84,12 @@ int live_rc6_manual(void *arg)
 	}
 
 	if (has_power) {
-		rc0_power = div64_u64(NSEC_PER_SEC * rc0_power,
-				      ktime_to_ns(dt));
-		if (!rc0_power) {
+		rc0_power[2] = div64_u64(NSEC_PER_SEC * rc0_power[1],
+					 ktime_to_ns(dt));
+
+		if (!rc0_power[2]) {
 			if (rc0_freq)
-				pr_debug("No power measured while in RC0! GPU Freq: %u in RC0\n",
+				pr_debug("No power measured while in RC0! GPU Freq: %uMHz in RC0\n",
 					 rc0_freq);
 			else
 				pr_err("No power and freq measured while in RC0\n");
@@ -98,10 +104,10 @@ int live_rc6_manual(void *arg)
 	res[0] = rc6_residency(rc6);
 	intel_uncore_forcewake_flush(rc6_to_uncore(rc6), FORCEWAKE_ALL);
 	dt = ktime_get();
-	rc6_power = librapl_energy_uJ();
-	msleep(1000);
+	rc6_power[0] = librapl_energy_uJ();
+	msleep(sleep_time);
 	rc6_freq = intel_rps_read_actual_frequency_fw(rps);
-	rc6_power = librapl_energy_uJ() - rc6_power;
+	rc6_power[1] = librapl_energy_uJ() - rc6_power[0];
 	dt = ktime_sub(ktime_get(), dt);
 	res[1] = rc6_residency(rc6);
 	if (res[1] == res[0]) {
@@ -112,14 +118,27 @@ int live_rc6_manual(void *arg)
 		err = -EINVAL;
 	}
 
+	diff = res[1] - res[0];
+	threshold = (9 * NSEC_PER_MSEC * sleep_time) / 10;
+	if (diff < threshold) {
+		pr_err("Did not enter RC6 properly, RC6 start residency=%lluns, RC6 end residency=%lluns\n",
+		       res[0], res[1]);
+		err = -EINVAL;
+	}
+
 	if (has_power) {
-		rc6_power = div64_u64(NSEC_PER_SEC * rc6_power,
-				      ktime_to_ns(dt));
-		pr_info("GPU consumed %llduW in RC0 and %llduW in RC6\n",
-			rc0_power, rc6_power);
-		if (2 * rc6_power > rc0_power) {
-			pr_err("GPU leaked energy while in RC6! GPU Freq: %u in RC6 and %u in RC0\n",
-			       rc6_freq, rc0_freq);
+		rc6_power[2] = div64_u64(NSEC_PER_SEC * rc6_power[1],
+					 ktime_to_ns(dt));
+		pr_info("GPU consumed %lluuW in RC0 and %lluuW in RC6\n",
+			rc0_power[2], rc6_power[2]);
+
+		if (2 * rc6_power[2] > rc0_power[2]) {
+			pr_err("GPU leaked energy while in RC6!\n"
+			       "GPU Freq: %uMHz in RC6 and %uMHz in RC0\n"
+			       "RC0 energy before & after sleep respectively: %lluuJ %lluuJ\n"
+			       "RC6 energy before & after sleep respectively: %lluuJ %lluuJ\n",
+			       rc6_freq, rc0_freq, rc0_power[0], rc0_power[1],
+			       rc6_power[0], rc6_power[1]);
 			err = -EINVAL;
 			goto out_unlock;
 		}
-- 
2.34.1