linux-kernel - [PATCH v4] PM: sleep: core: Avoid setting power.must

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Date:   Mon, 23 Aug 2021 08:27:50 -0700
From:   Prasad Sodagudi <psodagud@...eaurora.org>
To:     gregkh@...uxfoundation.org, rjw@...ysocki.net
Cc:     len.brown@...el.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, pavel@....cz, psodagud@...eaurora.org
Subject: [PATCH v4] PM: sleep: core: Avoid setting power.must_resume to false

There are variables(power.may_skip_resume and dev->power.must_resume)
and DPM_FLAG_MAY_SKIP_RESUME flags to control the resume of devices after
a system wide suspend transition.

Setting the DPM_FLAG_MAY_SKIP_RESUME flag means that the driver allows
its "noirq" and "early" resume callbacks to be skipped if the device
can be left in suspend after a system-wide transition into the working
state. PM core determines that the driver's "noirq" and "early" resume
callbacks should be skipped or not with dev_pm_skip_resume() function by
checking power.may_skip_resume variable.

power.must_resume variable is getting set to false in __device_suspend()
function without checking device's DPM_FLAG_MAY_SKIP_RESUME settings.
In problematic scenario, where all the devices in the suspend_late
stage are successful and some device can fail to suspend in
suspend_noirq phase. So some devices successfully suspended in suspend_late
stage are not getting chance to execute __device_suspend_noirq()
to set dev->power.must_resume variable to true and not getting
resumed in early_resume phase.

Add a check for device's DPM_FLAG_MAY_SKIP_RESUME flag before
setting power.must_resume variable in __device_suspend function.

Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase")
Signed-off-by: Prasad Sodagudi <psodagud@...eaurora.org>
---
 V3 -> V4: Remove dev->power.usage_count variable check
 V2 -> V3: Format issues patch posting
 V1 -> V2: Fixed indentation and commit text to include scenario
 drivers/base/power/main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index d568772..50e8ea3 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1642,7 +1642,10 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	}

 	dev->power.may_skip_resume = true;
-	dev->power.must_resume = false;
+	if (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME))
+		dev->power.must_resume = false;
+	else
+		dev->power.must_resume = true;

 	dpm_watchdog_set(&wd, dev);
 	device_lock(dev);
-- 
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