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 c0cc0dd78c7c8c1090e15d548bb8359cb5352122..84e77e8dbba19c5e543bcf8f63c3b282530b38af 100644 (file)
--- 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;