[Intel-gfx] [PATCH] drm/i915/pmu: Correct the rc6 offset upon enabling

[Chris Wilson]

The rc6 residency starts ticking from 0 from BIOS POST, but the kernel
starts measuring the time from its boot. If we start measuruing
I915_PMU_RC6_RESIDENCY while the GT is idle, we start our sampling from
0 and then upon first activity (park/unpark) add in all the rc6
residency since boot. After the first park with the sampler engaged, the
sleep/active counters are aligned.

Fixes: df6a42053513 ("drm/i915/pmu: Ensure monotonic rc6")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_pmu.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 28a82c849bac..fe0f3e0aa4ce 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -648,6 +648,13 @@ static void i915_pmu_enable(struct perf_event *event)
 	BUILD_BUG_ON(ARRAY_SIZE(pmu->enable_count) != I915_PMU_MASK_BITS);
 	GEM_BUG_ON(bit >= ARRAY_SIZE(pmu->enable_count));
 	GEM_BUG_ON(pmu->enable_count[bit] == ~0);
+
+	if (pmu->enable_count[bit] == 0 &&
+	    config_enabled_mask(I915_PMU_RC6_RESIDENCY) & BIT_ULL(bit)) {
+		pmu->sample[__I915_SAMPLE_RC6].cur = __get_rc6(&i915->gt);
+		pmu->sleep_last = ktime_get();
+	}
+
 	pmu->enable |= BIT_ULL(bit);
 	pmu->enable_count[bit]++;
 
-- 
2.25.0.rc2