[igt-dev] [PATCH i-g-t] i915/perf_pmu: Check that while parked, we report min freq or below

[Chris Wilson <chris@chris-wilson.co.uk>]

While the HW is parked, the GPU should be turned off and clocks stop
(i.e. running at 0Hz). We should report either the last frequency we
program (which should be the minimum legal value) or a more truthful 0.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 tests/perf_pmu.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index 54842784c..a1520d2c4 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -1477,6 +1477,44 @@ test_frequency(int gem_fd)
 	__assert_within_epsilon(max[0], max_freq, tolerance, 0.15f);
 }
 
+static void
+test_frequency_idle(int gem_fd)
+{
+	uint32_t min_freq;
+	uint64_t val[2], start[2], slept;
+	double idle[2];
+	int fd, sysfs;
+
+	sysfs = igt_sysfs_open(gem_fd);
+	igt_require(sysfs >= 0);
+
+	min_freq = igt_sysfs_get_u32(sysfs, "gt_RPn_freq_mhz");
+	close(sysfs);
+
+	/* While parked, our convention is to report the GPU at 0Hz */
+
+	fd = open_group(I915_PMU_REQUESTED_FREQUENCY, -1);
+	open_group(I915_PMU_ACTUAL_FREQUENCY, fd);
+
+	gem_quiescent_gpu(gem_fd); /* Be idle! */
+	measured_usleep(2000); /* Wait for timers to cease */
+
+	slept = pmu_read_multi(fd, 2, start);
+	measured_usleep(batch_duration_ns / 1000);
+	slept = pmu_read_multi(fd, 2, val) - slept;
+
+	idle[0] = 1e9*(val[0] - start[0]) / slept;
+	idle[1] = 1e9*(val[1] - start[1]) / slept;
+
+	igt_info("Idle frequency: requested %.1f, actual %.1f; HW min %u\n",
+		 idle[0], idle[1], min_freq);
+
+	igt_assert_f(idle[0] <= min_freq,
+		     "Request frequency should be 0 while parked!\n");
+	igt_assert_f(idle[1] <= min_freq,
+		     "Actual frequency should be 0 while parked!\n");
+}
+
 static bool wait_for_rc6(int fd)
 {
 	struct timespec tv = {};
@@ -1967,6 +2005,8 @@ igt_main
 	 */
 	igt_subtest("frequency")
 		test_frequency(fd);
+	igt_subtest("frequency-idle")
+		test_frequency_idle(fd);
 
 	/**
 	 * Test interrupt count reporting.
-- 
2.24.0

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