linux-kernel - [PATCH] cpuidle: undelaying cpuidle in dpm

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Message-Id: <20191029073145.154869-1-ikjn@chromium.org>
Date:   Tue, 29 Oct 2019 15:31:45 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     linux-pm@...r.kernel.org
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        "Pavel Machek )" <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Ikjoon Jang <ikjn@...omium.org>
Subject: [PATCH] cpuidle: undelaying cpuidle in dpm_{suspend|resume}()

cpuidle is paused only during dpm_suspend_noirq() ~ dpm_resume_noirq().
But some device drivers need random sized IOs in dpm_{suspend|resume}()
stage (e.g. re-downloading firmware in resume).
And with such a device, cpuidle's latencies could be critical to
response time of system suspend/resume.

To minimize those latencies, we could apply pm_qos to such device drivers,
but simply undelaying cpuidle from dpm_suspend_noirq() to dpm suspend()
seems no harm.
---
 drivers/base/power/main.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 134a8af51511..5928dd2139e8 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -773,8 +773,6 @@ void dpm_resume_noirq(pm_message_t state)
 
 	resume_device_irqs();
 	device_wakeup_disarm_wake_irqs();
-
-	cpuidle_resume();
 }
 
 static pm_callback_t dpm_subsys_resume_early_cb(struct device *dev,
@@ -1069,6 +1067,7 @@ void dpm_resume(pm_message_t state)
 
 	cpufreq_resume();
 	devfreq_resume();
+	cpuidle_resume();
 	trace_suspend_resume(TPS("dpm_resume"), state.event, false);
 }
 
@@ -1411,8 +1410,6 @@ int dpm_suspend_noirq(pm_message_t state)
 {
 	int ret;
 
-	cpuidle_pause();
-
 	device_wakeup_arm_wake_irqs();
 	suspend_device_irqs();
 
@@ -1830,6 +1827,7 @@ int dpm_suspend(pm_message_t state)
 	trace_suspend_resume(TPS("dpm_suspend"), state.event, true);
 	might_sleep();
 
+	cpuidle_pause();
 	devfreq_suspend();
 	cpufreq_suspend();
 
-- 
2.24.0.rc0.303.g954a862665-goog