Commit 985458d7 authored by Chris Wilson's avatar Chris Wilson Committed by Daniel Vetter
Browse files

drm/i915/selftest: Synchronise with the GPU timestamp 



Wait for the GPU to wake up from the semaphore before measuring the
time, so that we coordinate the sampling on both the CPU and GPU for
more accurate comparisons.

v2: Switch to local_irq_disable() as once suggested by Mika.

Reported-by: default avatarBruce Chang <yu.bruce.chang@intel.com>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: CQ Tang <cq.tang@intel.com>
Reviewed-by: default avatarBruce Chang <yu.bruce.chang@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210205112912.22978-1-chris@chris-wilson.co.uk


Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent dc430400

drivers/gpu/drm/i915/gt/selftest_engine_pm.c

+5 −3
Original line number Diff line number Diff line
@@ -110,13 +110,15 @@ static int __measure_timestamps(struct intel_context *ce, 
		cpu_relax();



	/* Run the request for a 100us, sampling timestamps before/after */

	preempt_disable();

	*dt = local_clock();

	local_irq_disable();

	write_semaphore(&sema[2], 0);

	while (READ_ONCE(sema[1]) == 0) /* wait for the gpu to catch up */

		cpu_relax();

	*dt = local_clock();

	udelay(100);

	*dt = local_clock() - *dt;

	write_semaphore(&sema[2], 1);

	preempt_enable();

	local_irq_enable();



	if (i915_request_wait(rq, 0, HZ / 2) < 0) {

		i915_request_put(rq);