[Intel-gfx] [PATCH] drm/i915/selftest: Fix gt_pm live_gt_clocks test

[Anshuman Gupta]

While reading the engine timestamps there can be uncontrollable
concurrent mmio access via other i915 child drivers and by GuC,
which may cause mmio latency to read the engine timestamps,
Account such latency to calculate time to read engine timestamp.

Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
---
 drivers/gpu/drm/i915/gt/selftest_gt_pm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
index be94f863bdef..4f299590ae62 100644
--- a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
@@ -50,8 +50,8 @@ static void measure_clocks(struct intel_engine_cs *engine,
 
 		udelay(1000);
 
-		dt[i] = ktime_sub(ktime_get(), dt[i]);
 		cycles[i] += ENGINE_READ_FW(engine, RING_TIMESTAMP);
+		dt[i] = ktime_sub(ktime_get(), dt[i]);
 		local_irq_enable();
 	}
 
-- 
2.25.1