linux-kernel - [PATCH 08/14] PM: domains: Measure suspend/resume latencies in genpd based on governor

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Date:   Wed, 11 May 2022 16:56:58 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Maulik Shah <quic_mkshah@...cinc.com>,
        Gabriel Fernandez <gabriel.fernandez@...s.st.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 08/14] PM: domains: Measure suspend/resume latencies in genpd based on governor

The QoS latency measurements for devices in genpd_runtime_suspend|resume()
are superfluous, unless the corresponding genpd has a governor assigned to
it, which would make use of the data.

Therefore, let's improve the behaviour in genpd by making the measurements
conditional, based upon if there's a governor assigned.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/base/power/domain.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4c059a858957..2cdfbe48dde0 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -881,7 +881,7 @@ static int genpd_runtime_suspend(struct device *dev)
 	struct generic_pm_domain_data *gpd_data = dev_gpd_data(dev);
 	struct gpd_timing_data *td = gpd_data->td;
 	bool runtime_pm = pm_runtime_enabled(dev);
-	ktime_t time_start;
+	ktime_t time_start = 0;
 	s64 elapsed_ns;
 	int ret;
 
@@ -902,8 +902,7 @@ static int genpd_runtime_suspend(struct device *dev)
 		return -EBUSY;
 
 	/* Measure suspend latency. */
-	time_start = 0;
-	if (runtime_pm)
+	if (td && runtime_pm)
 		time_start = ktime_get();
 
 	ret = __genpd_runtime_suspend(dev);
@@ -917,9 +916,9 @@ static int genpd_runtime_suspend(struct device *dev)
 	}
 
 	/* Update suspend latency value if the measured time exceeds it. */
-	if (runtime_pm) {
+	if (td && runtime_pm) {
 		elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));
-		if (td && (elapsed_ns > td->suspend_latency_ns)) {
+		if (elapsed_ns > td->suspend_latency_ns) {
 			td->suspend_latency_ns = elapsed_ns;
 			dev_dbg(dev, "suspend latency exceeded, %lld ns\n",
 				elapsed_ns);
@@ -956,11 +955,10 @@ static int genpd_runtime_resume(struct device *dev)
 	struct generic_pm_domain *genpd;
 	struct generic_pm_domain_data *gpd_data = dev_gpd_data(dev);
 	struct gpd_timing_data *td = gpd_data->td;
-	bool runtime_pm = pm_runtime_enabled(dev);
-	ktime_t time_start;
+	bool timed = td && pm_runtime_enabled(dev);
+	ktime_t time_start = 0;
 	s64 elapsed_ns;
 	int ret;
-	bool timed = true;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
@@ -988,8 +986,7 @@ static int genpd_runtime_resume(struct device *dev)
 
  out:
 	/* Measure resume latency. */
-	time_start = 0;
-	if (timed && runtime_pm)
+	if (timed)
 		time_start = ktime_get();
 
 	ret = genpd_start_dev(genpd, dev);
@@ -1001,9 +998,9 @@ static int genpd_runtime_resume(struct device *dev)
 		goto err_stop;
 
 	/* Update resume latency value if the measured time exceeds it. */
-	if (timed && runtime_pm) {
+	if (timed) {
 		elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));
-		if (td && (elapsed_ns > td->resume_latency_ns)) {
+		if (elapsed_ns > td->resume_latency_ns) {
 			td->resume_latency_ns = elapsed_ns;
 			dev_dbg(dev, "resume latency exceeded, %lld ns\n",
 				elapsed_ns);
-- 
2.25.1