From: Chris Wilson Date: Fri, 5 Feb 2021 11:29:12 +0000 (+0000) Subject: drm/i915/selftest: Synchronise with the GPU timestamp X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=985458d706bd86c16234bfc155535da2a64a9dde;p=linux.git 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: Bruce Chang Signed-off-by: Chris Wilson Cc: CQ Tang Reviewed-by: Bruce Chang Link: https://patchwork.freedesktop.org/patch/msgid/20210205112912.22978-1-chris@chris-wilson.co.uk Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c index 41dc1a542cd69..2c898622bdfb4 100644 --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c @@ -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);