tests/perf: prevent power management to kick in when necessary

Some of our tests measure that the OA unit produces reports at
expected time intervals (as configured through the PERF_OPEN
ioctl). It turns out the power management plays a role in the decision
of the OA unit to write reports to memory. Under normal circumstances
we don't really mind if the unit misses one report here or there, but
for our tests it makes pretty difficult to verify whether we've made a
mistake in the configuration.

To work around this, let's prevent power management to kick in by
holding /dev/cpu_dma_latency opened for the following tests :

  - enable-disable
  - blocking
  - polling
  - buffer-fill
  - oa-exponents

Many thanks to Chris Wilson for suggesting this!

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

1 files changed, 41 insertions, 23 deletions

diff --git a/tests/perf.c b/tests/perf.c
index 36e6f2316..a8b000ec7 100644
--- a/tests/perf.c
+++ b/tests/perf.c
@@ -288,6 +288,7 @@ static bool hsw_undefined_a_counters[45] = {
 static bool gen8_undefined_a_counters[45];
 
 static int drm_fd = -1;
+static int pm_fd = -1;
 static int stream_fd = -1;
 static uint32_t devid;
 static int card = -1;
@@ -331,21 +332,38 @@ __perf_close(int fd)
 {
 	close(fd);
 	stream_fd = -1;
+
+	if (pm_fd >= 0) {
+		close(pm_fd);
+		pm_fd = -1;
+	}
 }
 
 static int
-__perf_open(int fd, struct drm_i915_perf_open_param *param)
+__perf_open(int fd, struct drm_i915_perf_open_param *param, bool prevent_pm)
 {
 	int ret;
+	int32_t pm_value = 0;
 
 	if (stream_fd >= 0)
 		__perf_close(stream_fd);
+	if (pm_fd >= 0) {
+		close(pm_fd);
+		pm_fd = -1;
+	}
 
 	ret = igt_ioctl(fd, DRM_IOCTL_I915_PERF_OPEN, param);
 
 	igt_assert(ret >= 0);
 	errno = 0;
 
+	if (prevent_pm) {
+		pm_fd = open("/dev/cpu_dma_latency", O_RDWR);
+		igt_assert(pm_fd >= 0);
+
+		igt_assert_eq(write(pm_fd, &pm_value, sizeof(pm_value)), sizeof(pm_value));
+	}
+
 	return ret;
 }
 
@@ -1257,7 +1275,7 @@ test_system_wide_paranoid(void)
 
 		igt_drop_root();
 
-		stream_fd = __perf_open(drm_fd, &param);
+		stream_fd = __perf_open(drm_fd, &param, false);
 		__perf_close(stream_fd);
 	}
 
@@ -1314,7 +1332,7 @@ test_invalid_oa_metric_set_id(void)
 
 	/* Check that we aren't just seeing false positives... */
 	properties[ARRAY_SIZE(properties) - 1] = test_metric_set_id;
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 	__perf_close(stream_fd);
 
 	/* There's no valid default OA metric set ID... */
@@ -1348,7 +1366,7 @@ test_invalid_oa_format_id(void)
 
 	/* Check that we aren't just seeing false positives... */
 	properties[ARRAY_SIZE(properties) - 1] = test_oa_format;
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 	__perf_close(stream_fd);
 
 	/* There's no valid default OA format... */
@@ -1512,7 +1530,7 @@ open_and_read_2_oa_reports(int format_id,
 		.properties_ptr = to_user_pointer(properties),
 	};
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	read_2_oa_reports(format_id, exponent,
 			  oa_report0, oa_report1, timer_only);
@@ -1916,7 +1934,7 @@ test_oa_exponents(void)
 				  oa_exponent_to_ns(exponent) / 1000.0,
 				  oa_exponent_to_ns(exponent) / (1000.0 * 1000.0));
 
-			stream_fd = __perf_open(drm_fd, &param);
+			stream_fd = __perf_open(drm_fd, &param, true /* prevent_pm */);
 
 			/* Right after opening the OA stream, read a
 			 * first timestamp as way to filter previously
@@ -2192,7 +2210,7 @@ test_invalid_oa_exponent(void)
 		.properties_ptr = to_user_pointer(properties),
 	};
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	__perf_close(stream_fd);
 
@@ -2246,7 +2264,7 @@ test_low_oa_exponent_permissions(void)
 	igt_fork(child, 1) {
 		igt_drop_root();
 
-		stream_fd = __perf_open(drm_fd, &param);
+		stream_fd = __perf_open(drm_fd, &param, false);
 		__perf_close(stream_fd);
 	}
 
@@ -2312,7 +2330,7 @@ test_per_context_mode_unprivileged(void)
 
 		properties[1] = ctx_id;
 
-		stream_fd = __perf_open(drm_fd, &param);
+		stream_fd = __perf_open(drm_fd, &param, false);
 		__perf_close(stream_fd);
 
 		drm_intel_gem_context_destroy(context);
@@ -2401,7 +2419,7 @@ test_blocking(void)
 	int64_t start, end;
 	int n = 0;
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, true /* prevent_pm */);
 
 	times(&start_times);
 
@@ -2565,7 +2583,7 @@ test_polling(void)
 	int64_t start, end;
 	int n = 0;
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, true /* prevent_pm */);
 
 	times(&start_times);
 
@@ -2742,7 +2760,7 @@ test_buffer_fill(void)
 
 	igt_assert(fill_duration < 1000000000);
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, true /* prevent_pm */);
 
 	for (int i = 0; i < 5; i++) {
 		bool overflow_seen;
@@ -2909,7 +2927,7 @@ test_enable_disable(void)
 	load_helper_init();
 	load_helper_run(HIGH);
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, true /* prevent_pm */);
 
 	for (int i = 0; i < 5; i++) {
 		int len;
@@ -3073,7 +3091,7 @@ test_short_reads(void)
 	ret = mprotect(pages + page_size, page_size, PROT_NONE);
 	igt_assert_eq(ret, 0);
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	nanosleep(&(struct timespec){ .tv_sec = 0, .tv_nsec = 5000000 }, NULL);
 
@@ -3146,7 +3164,7 @@ test_non_sampling_read_error(void)
 	int ret;
 	uint8_t buf[1024];
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	ret = read(stream_fd, buf, sizeof(buf));
 	igt_assert_eq(ret, -1);
@@ -3184,7 +3202,7 @@ test_disabled_read_error(void)
 	uint32_t buf[128] = { 0 };
 	int ret;
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	ret = read(stream_fd, buf, sizeof(buf));
 	igt_assert_eq(ret, -1);
@@ -3194,7 +3212,7 @@ test_disabled_read_error(void)
 
 
 	param.flags &= ~I915_PERF_FLAG_DISABLED;
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	read_2_oa_reports(test_oa_format,
 			  oa_exponent,
@@ -3246,7 +3264,7 @@ test_mi_rpc(void)
 	uint32_t *report32;
 	int ret;
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	drm_intel_bufmgr_gem_enable_reuse(bufmgr);
 
@@ -3432,7 +3450,7 @@ hsw_test_single_ctx_counters(void)
 		scratch_buf_memset(dst[0].bo, width, height, 0x00ff00ff);
 
 		igt_debug("opening i915-perf stream\n");
-		stream_fd = __perf_open(drm_fd, &param);
+		stream_fd = __perf_open(drm_fd, &param, false);
 
 		bo = drm_intel_bo_alloc(bufmgr, "mi_rpc dest bo", 4096, 64);
 
@@ -3684,7 +3702,7 @@ gen8_test_single_ctx_render_target_writes_a_counter(void)
 			scratch_buf_memset(dst[0].bo, width, height, 0x00ff00ff);
 
 			igt_debug("opening i915-perf stream\n");
-			stream_fd = __perf_open(drm_fd, &param);
+			stream_fd = __perf_open(drm_fd, &param, false);
 
 			bo = drm_intel_bo_alloc(bufmgr, "mi_rpc dest bo", 4096, 64);
 
@@ -4031,7 +4049,7 @@ test_rc6_disable(void)
 
 	igt_skip_on(!rc6_enabled());
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	n_events_start = read_debugfs_u64_record(drm_fd, "i915_drpc_info",
 						 "RC6 residency since boot");
@@ -4246,7 +4264,7 @@ test_create_destroy_userspace_config(void)
 
 	/* Try to use the new config */
 	properties[1] = config_id;
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 
 	/* Verify that destroying the config doesn't yield any error. */
 	i915_perf_remove_config(drm_fd, config_id);
@@ -4453,7 +4471,7 @@ test_i915_ref_count(void)
 	igt_debug("initial ref count with drm_fd open = %u\n", ref_count0);
 	igt_assert(ref_count0 > baseline);
 
-	stream_fd = __perf_open(drm_fd, &param);
+	stream_fd = __perf_open(drm_fd, &param, false);
 	ref_count1 = read_i915_module_ref();
 	igt_debug("ref count after opening i915 perf stream = %u\n", ref_count1);
 	igt_assert(ref_count1 > ref_count0);