From 4afe6d18a2206aea4c4b2243a80cd534fd704a70 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 21 Apr 2020 15:22:36 +0100
Subject: drm/i915/selftests: Disable C-states when measuring RPS frequency
Git-commit: cf9ba27840c26f649a90bb04db5b455d47810292
Patch-mainline: v5.8-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
 response

Let's isolate the impact of cpu frequency selection on determing the GPU
throughput in response to selection of RPS frequencies.

For real systems, we do have to be concerned with the impact of
integrating c-states, p-states and rp-states, but for the sake of
proving whether or not RPS works, one baby step at a time.

For the record, as one would hope, it does not seem to impact on the
measured performance, but we do it anyway to reduce the number of
variables. Later, we can extend the testing to encourage the the
cpu/pkg to try and sleep while the GPU is busy.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200421142236.8614-1-chris@chris-wilson.co.uk
Link: https://patchwork.freedesktop.org/patch/msgid/20200421142236.8614-1-chris@chris-wilson.co.uk
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/gt/selftest_rps.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c
index 395265121e43..e2afc2003caa 100644
--- a/drivers/gpu/drm/i915/gt/selftest_rps.c
+++ b/drivers/gpu/drm/i915/gt/selftest_rps.c
@@ -3,6 +3,7 @@
  * Copyright © 2020 Intel Corporation
  */
 
+#include <linux/pm_qos.h>
 #include <linux/sort.h>
 
 #include "intel_engine_pm.h"
@@ -14,6 +15,9 @@
 #include "selftests/igt_spinner.h"
 #include "selftests/librapl.h"
 
+/* Try to isolate the impact of cstates from determing frequency response */
+#define CPU_LATENCY 0 /* -1 to disable pm_qos, 0 to disable cstates */
+
 static void dummy_rps_work(struct work_struct *wrk)
 {
 }
@@ -406,6 +410,7 @@ int live_rps_frequency_cs(void *arg)
 	struct intel_gt *gt = arg;
 	struct intel_rps *rps = &gt->rps;
 	struct intel_engine_cs *engine;
+	struct pm_qos_request qos;
 	enum intel_engine_id id;
 	int err = 0;
 
@@ -421,6 +426,9 @@ int live_rps_frequency_cs(void *arg)
 	if (INTEL_GEN(gt->i915) < 8) /* for CS simplicity */
 		return 0;
 
+	if (CPU_LATENCY >= 0)
+		cpu_latency_qos_add_request(&qos, CPU_LATENCY);
+
 	intel_gt_pm_wait_for_idle(gt);
 	saved_work = rps->work.func;
 	rps->work.func = dummy_rps_work;
@@ -527,6 +535,9 @@ int live_rps_frequency_cs(void *arg)
 	intel_gt_pm_wait_for_idle(gt);
 	rps->work.func = saved_work;
 
+	if (CPU_LATENCY >= 0)
+		cpu_latency_qos_remove_request(&qos);
+
 	return err;
 }
 
@@ -536,6 +547,7 @@ int live_rps_frequency_srm(void *arg)
 	struct intel_gt *gt = arg;
 	struct intel_rps *rps = &gt->rps;
 	struct intel_engine_cs *engine;
+	struct pm_qos_request qos;
 	enum intel_engine_id id;
 	int err = 0;
 
@@ -551,6 +563,9 @@ int live_rps_frequency_srm(void *arg)
 	if (INTEL_GEN(gt->i915) < 8) /* for CS simplicity */
 		return 0;
 
+	if (CPU_LATENCY >= 0)
+		cpu_latency_qos_add_request(&qos, CPU_LATENCY);
+
 	intel_gt_pm_wait_for_idle(gt);
 	saved_work = rps->work.func;
 	rps->work.func = dummy_rps_work;
@@ -656,6 +671,9 @@ int live_rps_frequency_srm(void *arg)
 	intel_gt_pm_wait_for_idle(gt);
 	rps->work.func = saved_work;
 
+	if (CPU_LATENCY >= 0)
+		cpu_latency_qos_remove_request(&qos);
+
 	return err;
 }
 
-- 
2.28.0