[Intel-gfx] [PATCH] i915/selftest: Disable irq to calc eng timestamp

[Anshuman Gupta]

gt_pm selftest calculates engine ticks cycles and wall time
cycles by delta of respective engine elapsed TIMESTAMP and ktime
for period of 1000us.
It compares the engine ticks cycles with wall time cycles.

Disable local cpu interrupt so that interrupt handler
should not preempt the measure_clocks() to calculate
correct engine ticks cycles.

Suggested-by: Chris P Wilson <chris.p.wilson at intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
---
 drivers/gpu/drm/i915/gt/selftest_gt_pm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
index b9441217ca3d..9cf76398bdf5 100644
--- a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
@@ -43,6 +43,7 @@ static void measure_clocks(struct intel_engine_cs *engine,
 	int i;
 
 	for (i = 0; i < 5; i++) {
+		local_irq_disable();
 		preempt_disable();
 		cycles[i] = -ENGINE_READ_FW(engine, RING_TIMESTAMP);
 		dt[i] = ktime_get();
@@ -52,6 +53,7 @@ static void measure_clocks(struct intel_engine_cs *engine,
 		dt[i] = ktime_sub(ktime_get(), dt[i]);
 		cycles[i] += ENGINE_READ_FW(engine, RING_TIMESTAMP);
 		preempt_enable();
+		local_irq_enable();
 	}
 
 	/* Use the median of both cycle/dt; close enough */
-- 
2.26.2