Commit b319cc59 authored by Tvrtko Ursulin's avatar Tvrtko Ursulin Committed by Umesh Nerlige Ramappa
Browse files

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: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarUmesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: default avatarUmesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: default avatarAshutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230519154946.3751971-6-umesh.nerlige.ramappa@intel.com
parent da5d5167

drivers/gpu/drm/i915/i915_pmu.c

+10 −2
Original line number Diff line number Diff line
@@ -262,6 +262,8 @@ 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->unparked &= ~BIT(gt->info.id);

	if (pmu->unparked == 0)

		pmu->timer_enabled = pmu_needs_timer(pmu, false);



	spin_unlock_irq(&pmu->lock);
@@ -279,8 +281,11 @@ void i915_pmu_gt_unparked(struct intel_gt *gt) 
	/*

	 * Re-enable sampling timer when GPU goes active.

	 */

	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 */

drivers/gpu/drm/i915/i915_pmu.h

+4 −0
Original line number Diff line number Diff line
@@ -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.

	 */