[PATCH] tests: drm_fdinfo: Fix zero tolerance checks

[Janusz Krzysztofik]

When we expect an engine to be busy, we check if its reported busy time
falls within a +/-5% tolerance range of measurement time period.
However, when we expect the engine to be idle, we compare its reported
busy time against zero, still with a +/-5% tolerance range, but now
calculated against the zero value, then no tolerance at all.  Obviously,
such check fails when the reported busy time is not exactly zero.

Compare engine idle time against measurement time period instead of
comparing its busy time against zero when we expect the busy time to be
close to zero.  As a debugging aid, display messages with the compared
values when requested via --debug option or when a failure occurs.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/7742
Suggested-by: Chris Wilson <chris.p.wilson at linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
---
 tests/intel/drm_fdinfo.c | 51 ++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 26 deletions(-)

diff --git a/tests/intel/drm_fdinfo.c b/tests/intel/drm_fdinfo.c
index 43216a64e..45d17aaaa 100644
--- a/tests/intel/drm_fdinfo.c
+++ b/tests/intel/drm_fdinfo.c
@@ -107,12 +107,18 @@ static const char *engine_map[] = {
 };
 
 #define __assert_within_epsilon(x, ref, tol_up, tol_down) \
-	igt_assert_f((double)(x) <= (1.0 + (tol_up)) * (double)(ref) && \
-		     (double)(x) >= (1.0 - (tol_down)) * (double)(ref), \
-		     "'%s' != '%s' (%f not within +%.1f%%/-%.1f%% tolerance of %f)\n",\
-		     #x, #ref, (double)(x), \
-		     (tol_up) * 100.0, (tol_down) * 100.0, \
-		     (double)(ref))
+	do { \
+		igt_assert_f((double)(x) <= (1.0 + (tol_up)) * (double)(ref) && \
+			     (double)(x) >= (1.0 - (tol_down)) * (double)(ref), \
+			     "'%s' != '%s' (%f not within +%.1f%%/-%.1f%% tolerance of %f)\n",\
+			     #x, #ref, (double)(x), \
+			     (tol_up) * 100.0, (tol_down) * 100.0, \
+			     (double)(ref)); \
+		igt_debug("%f within +%.1f%%/-%.1f%% tolerance of %f\n",\
+			  (double)(x), \
+			  (tol_up) * 100.0, (tol_down) * 100.0, \
+			  (double)(ref)); \
+	} while (0)
 
 #define assert_within_epsilon(x, ref, tolerance) \
 	__assert_within_epsilon(x, ref, tolerance, tolerance)
@@ -241,10 +247,8 @@ single(int gem_fd, const intel_ctx_t *ctx,
 	else
 		end_spin(spin_fd, spin, FLAG_SYNC);
 
-	assert_within_epsilon(val,
-			      (flags & TEST_BUSY) && !(flags & TEST_ISOLATION) ?
-			      slept : 0.0f,
-			      tolerance);
+	assert_within_epsilon((flags & TEST_BUSY) && !(flags & TEST_ISOLATION) ? val : slept - val,
+			      slept, tolerance);
 
 	/* Check for idle after hang. */
 	if (flags & FLAG_HANG) {
@@ -255,7 +259,7 @@ single(int gem_fd, const intel_ctx_t *ctx,
 		slept = measured_usleep(batch_duration_ns / 1000);
 		val = read_engine_time(gem_fd, e->class) - val;
 
-		assert_within_epsilon(val, 0, tolerance);
+		assert_within_epsilon(slept - val, slept, tolerance);
 	}
 
 	igt_spin_free(spin_fd, spin);
@@ -328,11 +332,8 @@ busy_check_all(int gem_fd, const intel_ctx_t *ctx,
 
 	log_busy(num_classes, val);
 
-	for (i = 0; i < num_classes; i++) {
-		double target = i == e->class ? slept : 0.0f;
-
-		assert_within_epsilon(val[i], target, tolerance);
-	}
+	for (i = 0; i < num_classes; i++)
+		assert_within_epsilon(i == e->class ? val[i] : slept - val[i], slept, tolerance);
 
 	gem_quiescent_gpu(gem_fd);
 }
@@ -405,9 +406,9 @@ most_busy_check_all(int gem_fd, const intel_ctx_t *ctx,
 	log_busy(num_classes, val);
 
 	for (i = 0; i < num_classes; i++) {
-		double target = slept * busy_class[i];
+		double target = slept * busy_class[i] ?: slept;
 
-		assert_within_epsilon(val[i], target, tolerance);
+		assert_within_epsilon(busy_class[i] ? val[i] : slept - val[i], target, tolerance);
 	}
 	gem_quiescent_gpu(gem_fd);
 }
@@ -460,9 +461,9 @@ all_busy_check_all(int gem_fd, const intel_ctx_t *ctx,
 	log_busy(num_classes, val);
 
 	for (i = 0; i < num_classes; i++) {
-		double target = slept * busy_class[i];
+		double target = slept * busy_class[i] ?: slept;
 
-		assert_within_epsilon(val[i], target, tolerance);
+		assert_within_epsilon(busy_class[i] ? val[i] : slept - val[i], target, tolerance);
 	}
 	gem_quiescent_gpu(gem_fd);
 }
@@ -601,10 +602,8 @@ virtual(int i915, const intel_ctx_cfg_t *base_cfg, unsigned int flags)
 			else
 				end_spin(i915, spin, FLAG_SYNC);
 
-			assert_within_epsilon(val,
-					      flags & TEST_BUSY ?
-					      slept : 0.0f,
-					      tolerance);
+			assert_within_epsilon(flags & TEST_BUSY ? val : slept - val,
+					      slept, tolerance);
 
 			/* Check for idle after hang. */
 			if (flags & FLAG_HANG) {
@@ -616,7 +615,7 @@ virtual(int i915, const intel_ctx_cfg_t *base_cfg, unsigned int flags)
 							1000);
 				val = read_engine_time(i915, class) - val;
 
-				assert_within_epsilon(val, 0, tolerance);
+				assert_within_epsilon(slept - val, slept, tolerance);
 			}
 
 			igt_spin_free(i915, spin);
@@ -724,7 +723,7 @@ virtual_all(int i915, const intel_ctx_cfg_t *base_cfg, unsigned int flags)
 						1000);
 			val = read_engine_time(i915, class) - val;
 
-			assert_within_epsilon(val, 0, tolerance);
+			assert_within_epsilon(slept - val, slept, tolerance);
 		}
 
 		igt_spin_free(i915, spin);
-- 
2.45.2