[PATCH v3] PM: sleep: core: Avoid setting power.must_resume to false

From: Prasad Sodagudi
Date: Tue Aug 10 2021 - 16:06:04 EST

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 and
dev->power.usage_count variables. 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@xxxxxxxxxxxxxx>
V2 -> V3: Format issues patch posting
V1 -> V2: Fixed indentation and commit text to include scenario
drivers/base/power/main.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index d568772..9ee6987 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1642,7 +1642,11 @@ 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 ((atomic_read(&dev->power.usage_count) <= 1) &&
+ (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);
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project