From: Anshuman Gupta <anshuman.gupta@intel.com>
Date: Thu, 23 Feb 2023 10:05:03 +0000 (+0530)
Subject: drm/i915/selftest: Fix ktime_get() and h/w access order
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4d14d7717f19fb1125496b1fd836ca89f11d540f;p=linux.git

drm/i915/selftest: Fix ktime_get() and h/w access order

Use ktime_get() after accessing the mmio or any driver resource,
while using wall time for various calculation that depends on
the inserted delay in order to account any mmio and resource
access latency.

Cc: Chris Wilson <chris.p.wilson@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230223100503.3323627-3-anshuman.gupta@intel.com
---

diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c
index c0cc0dd78c7c8..84e77e8dbba19 100644
--- a/drivers/gpu/drm/i915/gt/selftest_rps.c
+++ b/drivers/gpu/drm/i915/gt/selftest_rps.c
@@ -537,8 +537,8 @@ static u64 __measure_frequency(u32 *cntr, int duration_ms)
 {
 	u64 dc, dt;
 
-	dt = ktime_get();
 	dc = READ_ONCE(*cntr);
+	dt = ktime_get();
 	usleep_range(1000 * duration_ms, 2000 * duration_ms);
 	dc = READ_ONCE(*cntr) - dc;
 	dt = ktime_get() - dt;
@@ -566,8 +566,8 @@ static u64 __measure_cs_frequency(struct intel_engine_cs *engine,
 {
 	u64 dc, dt;
 
-	dt = ktime_get();
 	dc = intel_uncore_read_fw(engine->uncore, CS_GPR(0));
+	dt = ktime_get();
 	usleep_range(1000 * duration_ms, 2000 * duration_ms);
 	dc = intel_uncore_read_fw(engine->uncore, CS_GPR(0)) - dc;
 	dt = ktime_get() - dt;
@@ -1094,8 +1094,8 @@ static u64 __measure_power(int duration_ms)
 {
 	u64 dE, dt;
 
-	dt = ktime_get();
 	dE = librapl_energy_uJ();
+	dt = ktime_get();
 	usleep_range(1000 * duration_ms, 2000 * duration_ms);
 	dE = librapl_energy_uJ() - dE;
 	dt = ktime_get() - dt;