linux-kernel - [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support

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Message-Id: <20210929144451.113334-3-ulf.hansson@linaro.org>
Date:   Wed, 29 Sep 2021 16:44:51 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org
Cc:     Maulik Shah <mkshah@...eaurora.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Len Brown <len.brown@...el.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support

In the cpuidle-psci case, runtime PM in combination with the generic PM
domain (genpd), may be used when entering/exiting an idlestate. More
precisely, genpd relies on runtime PM to be enabled for the attached device
(in this case it belongs to a CPU), to properly manage the reference
counting of its PM domain.

This works fine most of the time, but during system suspend in the
dpm_suspend_late() phase, the PM core disables runtime PM for all devices.
Beyond this point and until runtime PM becomes re-enabled in the
dpm_resume_early() phase, calls to pm_runtime_get|put*() will fail.

To make sure the reference counting in genpd becomes correct, we need to
prevent cpuidle-psci from using runtime PM when it has been disabled for
the device. Therefore, let's move the call to cpuidle_pause() from
dpm_suspend_noirq() to dpm_suspend_late() - and cpuidle_resume() from
dpm_resume_noirq() into dpm_resume_early().

Diagnosed-by: Maulik Shah <mkshah@...eaurora.org>
Suggested-by: Maulik Shah <mkshah@...eaurora.org>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 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 cbea78e79f3d..1c753b651272 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -747,8 +747,6 @@ void dpm_resume_noirq(pm_message_t state)

 	resume_device_irqs();
 	device_wakeup_disarm_wake_irqs();
-
-	cpuidle_resume();
 }

 /**
@@ -870,6 +868,7 @@ void dpm_resume_early(pm_message_t state)
 	}
 	mutex_unlock(&dpm_list_mtx);
 	async_synchronize_full();
+	cpuidle_resume();
 	dpm_show_time(starttime, state, 0, "early");
 	trace_suspend_resume(TPS("dpm_resume_early"), state.event, false);
 }
@@ -1336,8 +1335,6 @@ int dpm_suspend_noirq(pm_message_t state)
 {
 	int ret;

-	cpuidle_pause();
-
 	device_wakeup_arm_wake_irqs();
 	suspend_device_irqs();

@@ -1467,6 +1464,7 @@ int dpm_suspend_late(pm_message_t state)
 	int error = 0;

 	trace_suspend_resume(TPS("dpm_suspend_late"), state.event, true);
+	cpuidle_pause();
 	mutex_lock(&dpm_list_mtx);
 	pm_transition = state;
 	async_error = 0;
-- 
2.25.1