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drm/i915/pmu: Add reference counting to the sampling timer 

We do not want to have timers per tile and waste CPU cycles and energy via
multiple wake-up sources, for a relatively un-important task of PMU
sampling, so keeping a single timer works well. But we also do not want
the first GT which goes idle to turn off the timer.

Add some reference counting, via a mask of unparked GTs, to solve this.

v2: Drop the check for unparked in i915_sample (Ashutosh)
v3: Revert v2 (Tvrtko)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230519154946.3751971-6-umesh.nerlige.ramappa@intel.com
This commit is contained in:
Tvrtko Ursulin 2023-05-19 08:49:44 -07:00 committed by Umesh Nerlige Ramappa
parent da5d516728
commit b319cc594e
2 changed files with 14 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/gpu/drm/i915/i915_pmu.c
View File

@ -262,7 +262,9 @@ void i915_pmu_gt_parked(struct intel_gt *gt)
* Signal sampling timer to stop if only engine events are enabled and
* GPU went idle.
*/
pmu->timer_enabled = pmu_needs_timer(pmu, false);
pmu->unparked &= ~BIT(gt->info.id);
if (pmu->unparked == 0)
pmu->timer_enabled = pmu_needs_timer(pmu, false);
spin_unlock_irq(&pmu->lock);
}
@ -279,7 +281,10 @@ void i915_pmu_gt_unparked(struct intel_gt *gt)
/*
* Re-enable sampling timer when GPU goes active.
*/
__i915_pmu_maybe_start_timer(pmu);
if (pmu->unparked == 0)
__i915_pmu_maybe_start_timer(pmu);
pmu->unparked |= BIT(gt->info.id);
spin_unlock_irq(&pmu->lock);
}
@ -449,6 +454,9 @@ static enum hrtimer_restart i915_sample(struct hrtimer *hrtimer)
*/
for_each_gt(gt, i915, i) {
if (!(pmu->unparked & BIT(i)))
continue;
engines_sample(gt, period_ns);
if (i == 0) /* FIXME */

4
drivers/gpu/drm/i915/i915_pmu.h
View File

@ -76,6 +76,10 @@ struct i915_pmu {
* @lock: Lock protecting enable mask and ref count handling.
*/
spinlock_t lock;
/**
* @unparked: GT unparked mask.
*/
unsigned int unparked;
/**
* @timer: Timer for internal i915 PMU sampling.
*/