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Message-ID: <aNL6TQ4vHtfoNE2d@lizhi-Precision-Tower-5810>
Date: Tue, 23 Sep 2025 15:51:41 -0400
From: Frank Li <Frank.li@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Linux PM <linux-pm@...r.kernel.org>, Takashi Iwai <tiwai@...e.de>,
LKML <linux-kernel@...r.kernel.org>,
Linux PCI <linux-pci@...r.kernel.org>,
Alex Williamson <alex.williamson@...hat.com>,
Bjorn Helgaas <helgaas@...nel.org>,
Zhang Qilong <zhangqilong3@...wei.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v3 1/3] PM: runtime: Add auto-cleanup macros for "resume
and get" operations
On Mon, Sep 22, 2025 at 05:30:43PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> It is generally useful to be able to automatically drop a device's
> runtime PM usage counter incremented by runtime PM operations that
> resume a device and bump up its usage counter [1].
>
> To that end, add DEFINE_CLASS() macros allowing pm_runtime_put()
> and pm_runtime_put_autosuspend() to be used for the auto-cleanup in
> those cases.
>
> Simply put, a piece of code like below:
>
> pm_runtime_get_sync(dev);
> .....
> pm_runtime_put(dev);
> return 0;
>
> can be transformed with CLASS(pm_runtime_get_sync) like:
>
> guard(pm_runtime_get_sync)(dev);
> .....
> return 0;
>
> (see pm_runtime_put() call is gone).
>
> However, it is better to do proper error handling in the majority of
> cases, so doing something like this instead of the above is recommended:
>
> CLASS(pm_runtime_get_active, pm)(dev);
> if (IS_ERR(pm))
> return PTR_ERR(pm);
> .....
> return 0;
>
> In all of the cases in which runtime PM is known to be enabled for the
> given device or the device can be regarded as operational (and so it can
> be accessed) with runtime PM disabled, a piece of code like:
>
> ret = pm_runtime_resume_and_get(dev);
> if (ret < 0)
> return ret;
> .....
> pm_runtime_put(dev);
> return 0;
>
> can be simplified with CLASS() like:
>
> CLASS(pm_runtime_get_active, pm)(dev);
> if (IS_ERR(pm))
> return PTR_ERR(pm);
> .....
> return 0;
>
> (again, see pm_runtime_put() call is gone).
>
> Still, if the device cannot be accessed unless runtime PM has been
> enabled for it, the CLASS(pm_runtime_get_active_enabled) variant
> needs to be used, that is (in the context of the example above):
>
> CLASS(pm_runtime_get_active_enabled, pm)(dev);
> if (IS_ERR(pm))
> return PTR_ERR(pm);
> .....
> return 0;
>
> When the original code calls pm_runtime_put_autosuspend(), use one
> of the "auto" class variants, CLASS(pm_runtime_get_active_auto) or
> CLASS(pm_runtime_get_active_enabled_auto), so for example, a piece
> of code like:
>
> ret = pm_runtime_resume_and_get(dev);
> if (ret < 0)
> return ret;
> .....
> pm_runtime_put_autosuspend(dev);
> return 0;
>
> will become:
>
> CLASS(pm_runtime_get_active_enabled_auto, pm)(dev);
> if (IS_ERR(pm))
> return PTR_ERR(pm);
> .....
> return 0;
>
> Note that the cases in which the return value of pm_runtime_get_sync()
> is checked can also be handled with the help of the new class macros.
> For example, a piece of code like:
>
> ret = pm_runtime_get_sync(dev);
> if (ret < 0) {
> pm_runtime_put(dev);
> return ret;
> }
> .....
> pm_runtime_put(dev);
> return 0;
>
> can be rewritten as:
>
> CLASS(pm_runtime_get_active_enabled, pm)(dev);
> if (IS_ERR(pm))
> return PTR_ERR(pm);
> .....
> return 0;
>
> or CLASS(pm_runtime_get_active) can be used if transparent handling of
> disabled runtime PM is desirable.
>
> Link: https://lore.kernel.org/linux-pm/878qimv24u.wl-tiwai@suse.de/ [1]
> Co-developed-by: Takashi Iwai <tiwai@...e.de>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
Nice feature.
Reviewed-by: Frank Li <Frank.Li@....com>
>
> v2 -> v3:
> * Two more class definitions for the case in which resume errors can be
> neglected.
> * Update of new code comments (for more clarity).
> * Changelog update.
>
> v1 -> v2:
> * Rename the new classes and the new static inline helper.
> * Add two classes for handling disabled runtime PM.
> * Expand the changelog.
> * Adjust the subject.
>
> ---
> drivers/base/power/runtime.c | 2 +
> include/linux/pm_runtime.h | 82 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 84 insertions(+)
>
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -796,6 +796,8 @@ static int rpm_resume(struct device *dev
> if (dev->power.runtime_status == RPM_ACTIVE &&
> dev->power.last_status == RPM_ACTIVE)
> retval = 1;
> + else if (rpmflags & RPM_TRANSPARENT)
> + goto out;
> else
> retval = -EACCES;
> }
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -21,6 +21,7 @@
> #define RPM_GET_PUT 0x04 /* Increment/decrement the
> usage_count */
> #define RPM_AUTO 0x08 /* Use autosuspend_delay */
> +#define RPM_TRANSPARENT 0x10 /* Succeed if runtime PM is disabled */
>
> /*
> * Use this for defining a set of PM operations to be used in all situations
> @@ -533,6 +534,32 @@ static inline int pm_runtime_resume_and_
> }
>
> /**
> + * pm_runtime_get_active_dev - Resume a device and bump up its usage counter.
> + * @dev: Target device.
> + * @rpmflags: Additional runtime PM flags to combine with RPM_GET_PUT.
> + *
> + * Resume @dev synchronously and if that is successful, increment its runtime
> + * PM usage counter.
> + *
> + * Return:
> + * * 0 if the runtime PM usage counter of @dev has been incremented.
> + * * Negative error code otherwise.
> + */
> +static inline struct device *pm_runtime_get_active_dev(struct device *dev,
> + int rpmflags)
> +{
> + int ret;
> +
> + ret = __pm_runtime_resume(dev, RPM_GET_PUT | rpmflags);
> + if (ret < 0) {
> + pm_runtime_put_noidle(dev);
> + return ERR_PTR(ret);
> + }
> +
> + return dev;
> +}
> +
> +/**
> * pm_runtime_put - Drop device usage counter and queue up "idle check" if 0.
> * @dev: Target device.
> *
> @@ -606,6 +633,61 @@ static inline int pm_runtime_put_autosus
> return __pm_runtime_put_autosuspend(dev);
> }
>
> +/*
> + * The way to use the classes defined below is to define a class variable and
> + * use it going forward for representing the target device until it goes out of
> + * the scope. For example:
> + *
> + * CLASS(pm_runtime_get_active, active_dev)(dev);
> + * if (IS_ERR(active_dev))
> + * return PTR_ERR(active_dev);
> + *
> + * ... do something with active_dev (which is guaranteed to never suspend) ...
> + *
> + * If an error occurs, the runtime PM usage counter of dev will not be
> + * incremented, so using these classes without error handling is not
> + * recommended.
> + */
> +DEFINE_CLASS(pm_runtime_get_active, struct device *,
> + if (!IS_ERR_OR_NULL(_T)) pm_runtime_put(_T),
> + pm_runtime_get_active_dev(dev, RPM_TRANSPARENT), struct device *dev)
> +
> +DEFINE_CLASS(pm_runtime_get_active_auto, struct device *,
> + if (!IS_ERR_OR_NULL(_T)) pm_runtime_put_autosuspend(_T),
> + pm_runtime_get_active_dev(dev, RPM_TRANSPARENT), struct device *dev)
> +
> +/*
> + * The following two classes are analogous to the two classes defined above,
> + * respectively, but they produce an error pointer if runtime PM has been
> + * disabled for the given device.
> + *
> + * They should be used only when runtime PM may be disabled for the given device
> + * and if that happens, the device is not regarded as operational and so it
> + * cannot be accessed. The classes defined above should be used instead in all
> + * of the other cases.
> + */
> +DEFINE_CLASS(pm_runtime_get_active_enabled, struct device *,
> + if (!IS_ERR_OR_NULL(_T)) pm_runtime_put(_T),
> + pm_runtime_get_active_dev(dev, 0), struct device *dev)
> +
> +DEFINE_CLASS(pm_runtime_get_active_enabled_auto, struct device *,
> + if (!IS_ERR_OR_NULL(_T)) pm_runtime_put_autosuspend(_T),
> + pm_runtime_get_active_dev(dev, 0), struct device *dev)
> +
> +/*
> + * The following classes may be used instead of the above if resume failures can
> + * be neglected. However, such cases are not expected to be prevalent, so using
> + * one of these classes should always be regarded as an exception and explained
> + * in an adjacent code comment.
> + */
> +DEFINE_CLASS(pm_runtime_get_sync, struct device *,
> + if (_T) pm_runtime_put(_T),
> + ({ pm_runtime_get_sync(dev); dev; }), struct device *dev)
> +
> +DEFINE_CLASS(pm_runtime_get_sync_auto, struct device *,
> + if (_T) pm_runtime_put_autosuspend(_T),
> + ({ pm_runtime_get_sync(dev); dev; }), struct device *dev)
> +
> /**
> * pm_runtime_put_sync - Drop device usage counter and run "idle check" if 0.
> * @dev: Target device.
>
>
>
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