In our tests where we measure the elapsed time on both the CPU and CS using a udelay, our CS results match the udelay much more accurately than the ktime (even when using ktime_get_fast_ns). With preemption disabled, we can go one step lower than ktime and use local_clock.
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2919 Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Reviewed-by: Andi Shyti <andi.sh...@intel.com> --- drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c index ca080445695e..c3d965279fc3 100644 --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c @@ -112,11 +112,11 @@ static int __measure_timestamps(struct intel_context *ce, /* Run the request for a 100us, sampling timestamps before/after */ preempt_disable(); - *dt = ktime_get_raw_fast_ns(); + *dt = local_clock(); write_semaphore(&sema[2], 0); udelay(100); + *dt = local_clock() - *dt; write_semaphore(&sema[2], 1); - *dt = ktime_get_raw_fast_ns() - *dt; preempt_enable(); if (i915_request_wait(rq, 0, HZ / 2) < 0) { -- 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
