[igt-dev] [PATCH i-g-t] i915/perf: Add test to query CS timestamp

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

Add tests to query CS timestamps for different engines.

v2:
- remove flag parameter
- assert for minimum usable values rather than maximum

v3:
- use clock id for cpu timestamps (Lionel)
- check if query is supported (Ashutosh)
- test bad queries

v4: (Chris, Tvrtko)
- cs_timestamp is a misnomer, use cs_cycles instead
- use cs cycle frequency returned in the query
- omit size parameter

v5:
- use __for_each_physical_engine (Lionel)
- check for ENODEV (Umesh)

v6: Use 2 cpu timestamps to calculate reg read time (Lionel)
v7: Refactor test code and add a spinner (Chris)
v8: Update cpu_timestamp array split into timestamp and delta

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
---
 include/drm-uapi/i915_drm.h |  52 ++++++++++
 tests/i915/i915_query.c     | 190 ++++++++++++++++++++++++++++++++++++
 2 files changed, 242 insertions(+)

diff --git a/include/drm-uapi/i915_drm.h b/include/drm-uapi/i915_drm.h
index bf9ea471..1d1fe852 100644
--- a/include/drm-uapi/i915_drm.h
+++ b/include/drm-uapi/i915_drm.h
@@ -2176,6 +2176,10 @@ struct drm_i915_query_item {
 #define DRM_I915_QUERY_TOPOLOGY_INFO    1
 #define DRM_I915_QUERY_ENGINE_INFO	2
 #define DRM_I915_QUERY_PERF_CONFIG      3
+	/**
+	 * Query Command Streamer timestamp register.
+	 */
+#define DRM_I915_QUERY_CS_CYCLES	4
 /* Must be kept compact -- no holes and well documented */
 
 	/*
@@ -2309,6 +2313,54 @@ struct drm_i915_engine_info {
 	__u64 rsvd1[4];
 };
 
+/**
+ * struct drm_i915_query_cs_cycles
+ *
+ * The query returns the command streamer cycles, the frequency that can be
+ * used to calculate the command streamer timestamp, a cpu timestamp indicating
+ * when the cs cycles was captured and a cpu_delta capturing time taken to read
+ * the cs_cycles register.
+ */
+struct drm_i915_query_cs_cycles {
+	/** Engine for which command streamer cycles is queried. */
+	struct i915_engine_class_instance engine;
+
+	/** Must be zero. */
+	__u32 flags;
+
+	/**
+	 * Command streamer cycles as read from the command streamer
+	 * register at 0x358 offset.
+	 */
+	__u64 cs_cycles;
+
+	/** Frequency of the cs cycles in Hz. */
+	__u64 cs_frequency;
+
+	/**
+	 * CPU timestamp in ns. The timestamp is captured before reading the
+	 * cs_cycles register using the reference clockid set by the user.
+	 */
+	__u64 cpu_timestamp;
+
+	/**
+	 * Time delta in ns captured around reading the lower dword of the
+	 * cs_cycles register.
+	 */
+	__u64 cpu_delta;
+
+	/**
+	 * Reference clock id for CPU timestamp. For definition, see
+	 * clock_gettime(2) and perf_event_open(2). Supported clock ids are
+	 * CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW, CLOCK_REALTIME, CLOCK_BOOTTIME,
+	 * CLOCK_TAI.
+	 */
+	__s32 clockid;
+
+	/** Must be zero. */
+	__u32 rsvd;
+};
+
 /**
  * struct drm_i915_query_engine_info
  *
diff --git a/tests/i915/i915_query.c b/tests/i915/i915_query.c
index 29b938e9..3c6c5c54 100644
--- a/tests/i915/i915_query.c
+++ b/tests/i915/i915_query.c
@@ -267,6 +267,184 @@ eu_available(const struct drm_i915_query_topology_info *topo_info,
 				eu / 8] >> (eu % 8)) & 1;
 }
 
+static int __query_cs_cycles(int i915, void *data)
+{
+	struct drm_i915_query_item item = {
+		.query_id = DRM_I915_QUERY_CS_CYCLES,
+		.data_ptr = to_user_pointer(data),
+		.length = data ? sizeof(struct drm_i915_query_cs_cycles) : 0,
+	};
+
+	i915_query_items(i915, &item, 1);
+
+	return item.length;
+}
+
+static bool query_cs_cycles_supported(int fd)
+{
+	return __query_cs_cycles(fd, NULL) > 0;
+}
+
+static bool engine_has_cs_cycles(int i915, uint16_t class, uint16_t instance)
+{
+	struct drm_i915_query_cs_cycles ts = {
+		.engine = { class, instance }
+	};
+
+	return __query_cs_cycles(i915, &ts) != -ENODEV;
+}
+
+static void
+__cs_cycles(int i915, struct i915_engine_class_instance *engine)
+{
+	struct drm_i915_query_cs_cycles ts1 = {};
+	struct drm_i915_query_cs_cycles ts2 = {};
+	uint64_t delta_cpu, delta_cs, delta_delta;
+	int i, usable = 0;
+	igt_spin_t *spin;
+	uint32_t ctx;
+	struct {
+		int32_t id;
+		const char *name;
+	} clock[] = {
+		{ CLOCK_MONOTONIC, "CLOCK_MONOTONIC" },
+		{ CLOCK_MONOTONIC_RAW, "CLOCK_MONOTONIC_RAW" },
+		{ CLOCK_REALTIME, "CLOCK_REALTIME" },
+		{ CLOCK_BOOTTIME, "CLOCK_BOOTTIME" },
+		{ CLOCK_TAI, "CLOCK_TAI" },
+	};
+
+	igt_debug("engine[%u:%u]\n",
+		  engine->engine_class,
+		  engine->engine_instance);
+
+	ctx = gem_context_create_for_engine(i915,
+					    engine->engine_class,
+					    engine->engine_instance);
+	spin = igt_spin_new(i915, ctx);
+
+	/* Try a new clock every 10 iterations. */
+#define NUM_SNAPSHOTS 10
+	for (i = 0; i < NUM_SNAPSHOTS * ARRAY_SIZE(clock); i++) {
+		int index = i / NUM_SNAPSHOTS;
+
+		ts1.engine = *engine;
+		ts1.clockid = clock[index].id;
+
+		ts2.engine = *engine;
+		ts2.clockid = clock[index].id;
+
+		igt_assert_eq(__query_cs_cycles(i915, &ts1), sizeof(ts1));
+		igt_assert_eq(__query_cs_cycles(i915, &ts2), sizeof(ts2));
+
+		igt_debug("[1] cpu_ts before %llu, reg read time %llu\n",
+			  ts1.cpu_timestamp,
+			  ts1.cpu_delta);
+		igt_debug("[1] cs_ts %llu, freq %llu Hz\n",
+			  ts1.cs_cycles, ts1.cs_frequency);
+
+		igt_debug("[2] cpu_ts before %llu, reg read time %llu\n",
+			  ts2.cpu_timestamp,
+			  ts2.cpu_delta);
+		igt_debug("[2] cs_ts %llu, freq %llu Hz\n",
+			  ts2.cs_cycles, ts2.cs_frequency);
+
+		delta_cpu = ts2.cpu_timestamp - ts1.cpu_timestamp;
+		delta_cs = (ts2.cs_cycles - ts1.cs_cycles) *
+			   NSEC_PER_SEC / ts1.cs_frequency;
+
+		igt_debug("delta_cpu[%lu], delta_cs[%lu]\n",
+			  delta_cpu, delta_cs);
+
+		delta_delta = delta_cpu > delta_cs ?
+			       delta_cpu - delta_cs :
+			       delta_cs - delta_cpu;
+		igt_debug("delta_delta %lu\n", delta_delta);
+
+		if (delta_delta < 5000)
+			usable++;
+
+		/*
+		 * User needs few good snapshots of the timestamps to
+		 * synchronize cpu time with cs time. Check if we have enough
+		 * usable values before moving to the next clockid.
+		 */
+		if (!((i + 1) % NUM_SNAPSHOTS)) {
+			igt_debug("clock %s\n", clock[index].name);
+			igt_debug("usable %d\n", usable);
+			igt_assert(usable > 2);
+			usable = 0;
+		}
+	}
+
+	gem_context_destroy(i915, ctx);
+	igt_spin_free(i915, spin);
+}
+
+static void test_cs_cycles(int i915)
+{
+	const struct intel_execution_engine2 *e;
+	struct i915_engine_class_instance engine;
+
+	__for_each_physical_engine(i915, e) {
+		if (engine_has_cs_cycles(i915, e->class, e->instance)) {
+			engine.engine_class = e->class;
+			engine.engine_instance = e->instance;
+			__cs_cycles(i915, &engine);
+		}
+	}
+}
+
+static void test_cs_cycles_invalid(int i915)
+{
+	struct i915_engine_class_instance engine;
+	const struct intel_execution_engine2 *e;
+	struct drm_i915_query_cs_cycles ts = {};
+
+	/* get one engine */
+	__for_each_physical_engine(i915, e)
+		break;
+
+	/* sanity check engine selection is valid */
+	ts.engine.engine_class = e->class;
+	ts.engine.engine_instance = e->instance;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), sizeof(ts));
+
+	/* bad engines */
+	ts.engine.engine_class = e->class;
+	ts.engine.engine_instance = -1;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	ts.engine.engine_class = -1;
+	ts.engine.engine_instance = e->instance;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	ts.engine.engine_class = -1;
+	ts.engine.engine_instance = -1;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	/* non zero flags */
+	ts.flags = 1;
+	ts.engine.engine_class = e->class;
+	ts.engine.engine_instance = e->instance;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	/* non zero rsvd field */
+	ts.flags = 0;
+	ts.rsvd = 1;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	/* bad clockid */
+	ts.rsvd = 0;
+	ts.clockid = -1;
+	igt_assert_eq(__query_cs_cycles(i915, &ts), -EINVAL);
+
+	/* sanity check */
+	engine.engine_class = e->class;
+	engine.engine_instance = e->instance;
+	__cs_cycles(i915, &engine);
+}
+
 /*
  * Verify that we get coherent values between the legacy getparam slice/subslice
  * masks and the new topology query.
@@ -783,6 +961,18 @@ igt_main
 			engines(fd);
 	}
 
+	igt_subtest_group {
+		igt_fixture {
+			igt_require(query_cs_cycles_supported(fd));
+		}
+
+		igt_subtest("cs-cycles-invalid")
+			test_cs_cycles_invalid(fd);
+
+		igt_subtest("cs-cycles")
+			test_cs_cycles(fd);
+	}
+
 	igt_fixture {
 		close(fd);
 	}
-- 
2.20.1

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