[PATCH v5] PM: sleep: core: Avoid setting power.must_resume to false

[PATCH v5] PM: sleep: core: Avoid setting power.must_resume to false

[Prasad Sodagudi]

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@codeaurora.org>
---
 V4 -> V5: Fix coding style
 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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index d568772..cbea78e 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1642,7 +1642,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	}
 
 	dev->power.may_skip_resume = true;
-	dev->power.must_resume = false;
+	dev->power.must_resume = !dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME);
 
 	dpm_watchdog_set(&wd, dev);
 	device_lock(dev);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v5] PM: sleep: core: Avoid setting power.must_resume to false

[Rafael J. Wysocki]

On Tue, Sep 7, 2021 at 1:24 PM Prasad Sodagudi <psodagud@codeaurora.org> wrote:
>
> 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@codeaurora.org>
> ---
>  V4 -> V5: Fix coding style
>  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 | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index d568772..cbea78e 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1642,7 +1642,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>         }
>
>         dev->power.may_skip_resume = true;
> -       dev->power.must_resume = false;
> +       dev->power.must_resume = !dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME);
>
>         dpm_watchdog_set(&wd, dev);
>         device_lock(dev);
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project

Applied as 5.15-rc material, thanks!