linux-kernel - Re: [PATCH v2] PM: sleep: Adjust check before setting power.must

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Message-ID: <CAPDyKFoQvKFmwpzPtHGzPKzPv7KLo_7-2oYb2=BXEZAm4xpVbQ@mail.gmail.com>
Date: Mon, 3 Mar 2025 12:49:52 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Alan Stern <stern@...land.harvard.edu>, Johan Hovold <johan@...nel.org>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH v2] PM: sleep: Adjust check before setting power.must_resume

On Thu, 27 Feb 2025 at 11:53, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> The check before setting power.must_resume in device_suspend_noirq()
> does not take power.child_count into account, but it should do that, so
> use pm_runtime_need_not_resume() in it for this purpose and adjust the
> comment next to it accordingly.
>
> Fixes: 107d47b2b95e ("PM: sleep: core: Simplify the SMART_SUSPEND flag handling")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>
> The previous version of this patch is here:
>
> https://lore.kernel.org/linux-pm/3548152.QJadu78ljV@rjwysocki.net/
>
> v1 -> v2:
>    * Changelog rewrite.
>    * Added the Fixes: tag.
>    * Refined the comment adjustment.
>
> ---
>  drivers/base/power/main.c    |   13 ++++++-------
>  drivers/base/power/runtime.c |    2 +-
>  include/linux/pm_runtime.h   |    2 ++
>  3 files changed, 9 insertions(+), 8 deletions(-)
>
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1382,14 +1382,13 @@
>         dev->power.is_noirq_suspended = true;
>
>         /*
> -        * Skipping the resume of devices that were in use right before the
> -        * system suspend (as indicated by their PM-runtime usage counters)
> -        * would be suboptimal.  Also resume them if doing that is not allowed
> -        * to be skipped.
> +        * Devices must be resumed unless they are explicitly allowed to be left
> +        * in suspend, but even in that case skipping the resume of devices that
> +        * were in use right before the system suspend (as indicated by their
> +        * runtime PM usage counters and child counters) would be suboptimal.
>          */
> -       if (atomic_read(&dev->power.usage_count) > 1 ||
> -           !(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
> -             dev->power.may_skip_resume))
> +       if (!(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
> +             dev->power.may_skip_resume) || !pm_runtime_need_not_resume(dev))
>                 dev->power.must_resume = true;
>
>         if (dev->power.must_resume)
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1897,7 +1897,7 @@
>         pm_request_idle(link->supplier);
>  }
>
> -static bool pm_runtime_need_not_resume(struct device *dev)
> +bool pm_runtime_need_not_resume(struct device *dev)
>  {
>         return atomic_read(&dev->power.usage_count) <= 1 &&
>                 (atomic_read(&dev->power.child_count) == 0 ||
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -66,6 +66,7 @@
>
>  extern int pm_generic_runtime_suspend(struct device *dev);
>  extern int pm_generic_runtime_resume(struct device *dev);
> +extern bool pm_runtime_need_not_resume(struct device *dev);
>  extern int pm_runtime_force_suspend(struct device *dev);
>  extern int pm_runtime_force_resume(struct device *dev);
>
> @@ -254,6 +255,7 @@
>
>  static inline int pm_generic_runtime_suspend(struct device *dev) { return 0; }
>  static inline int pm_generic_runtime_resume(struct device *dev) { return 0; }
> +static inline bool pm_runtime_need_not_resume(struct device *dev) {return true; }
>  static inline int pm_runtime_force_suspend(struct device *dev) { return 0; }
>  static inline int pm_runtime_force_resume(struct device *dev) { return 0; }
>
>
>
>