Re: [PATCH 2/2] pm: runtime: Add pm_runtime_put_autosuspend() replacement

Laurent Pinchart
2024-01-09T16:40:39Z

Hi Sakari,

Thank you for the patch.

On Tue, Jan 09, 2024 at 03:36:39PM +0200, Sakari Ailus wrote:
> Add __pm_runtime_put_autosuspend() that replaces
> pm_runtime_put_autosuspend() for new users. The intent is to later
> re-purpose pm_runtime_put_autosuspend() to also mark the device's last
> busy stamp---which is what the vast majority of users actually need.
>
> This is also described in pm_runtime_put_autosuspend() documentation.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

This looks good to me, so

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

Do you plan to patch the existing users tree-wide ?

> ---
> Documentation/power/runtime_pm.rst | 17 +++++++++++------
> include/linux/pm_runtime.h | 12 ++++++++++++
> 2 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst
> index da99379071a4..6fa50e4f87ce 100644
> --- a/Documentation/power/runtime_pm.rst
> +++ b/Documentation/power/runtime_pm.rst
> @@ -154,7 +154,7 @@ suspending the device are satisfied) and to queue up a suspend request for the
> device in that case. If there is no idle callback, or if the callback returns
> 0, then the PM core will attempt to carry out a runtime suspend of the device,
> also respecting devices configured for autosuspend. In essence this means a
> -call to pm_runtime_autosuspend() (do note that drivers needs to update the
> +call to __pm_runtime_autosuspend() (do note that drivers needs to update the
> device last busy mark, pm_runtime_mark_last_busy(), to control the delay under
> this circumstance). To prevent this (for example, if the callback routine has
> started a delayed suspend), the routine must return a non-zero value. Negative
> @@ -409,6 +409,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
> pm_request_idle(dev) and return its result
>
> `int pm_runtime_put_autosuspend(struct device *dev);`
> + - does the same as __pm_runtime_put_autosuspend() for now, but in the
> + future, will also call pm_runtime_mark_last_busy() as well, DO NOT USE!
> +
> + `int __pm_runtime_put_autosuspend(struct device *dev);`
> - decrement the device's usage counter; if the result is 0 then run
> pm_request_autosuspend(dev) and return its result
>
> @@ -539,6 +543,7 @@ It is safe to execute the following helper functions from interrupt context:
> - pm_runtime_put_noidle()
> - pm_runtime_put()
> - pm_runtime_put_autosuspend()
> +- __pm_runtime_put_autosuspend()
> - pm_runtime_enable()
> - pm_suspend_ignore_children()
> - pm_runtime_set_active()
> @@ -864,9 +869,9 @@ automatically be delayed until the desired period of inactivity has elapsed.
>
> Inactivity is determined based on the power.last_busy field. Drivers should
> call pm_runtime_mark_last_busy() to update this field after carrying out I/O,
> -typically just before calling pm_runtime_put_autosuspend(). The desired length
> -of the inactivity period is a matter of policy. Subsystems can set this length
> -initially by calling pm_runtime_set_autosuspend_delay(), but after device
> +typically just before calling __pm_runtime_put_autosuspend(). The desired
> +length of the inactivity period is a matter of policy. Subsystems can set this
> +length initially by calling pm_runtime_set_autosuspend_delay(), but after device
> registration the length should be controlled by user space, using the
> /sys/devices/.../power/autosuspend_delay_ms attribute.
>
> @@ -877,7 +882,7 @@ instead of the non-autosuspend counterparts::
>
> Instead of: pm_runtime_suspend use: pm_runtime_autosuspend;
> Instead of: pm_schedule_suspend use: pm_request_autosuspend;
> - Instead of: pm_runtime_put use: pm_runtime_put_autosuspend;
> + Instead of: pm_runtime_put use: __pm_runtime_put_autosuspend;
> Instead of: pm_runtime_put_sync use: pm_runtime_put_sync_autosuspend.
>
> Drivers may also continue to use the non-autosuspend helper functions; they
> @@ -916,7 +921,7 @@ Here is a schematic pseudo-code example::
> lock(&foo->private_lock);
> if (--foo->num_pending_requests == 0) {
> pm_runtime_mark_last_busy(&foo->dev);
> - pm_runtime_put_autosuspend(&foo->dev);
> + __pm_runtime_put_autosuspend(&foo->dev);
> } else {
> foo_process_next_request(foo);
> }
> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 13cd526634c1..d28df13ffe4d 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -482,6 +482,18 @@ static inline int pm_runtime_put(struct device *dev)
> return __pm_runtime_idle(dev, RPM_GET_PUT | RPM_ASYNC);
> }
>
> +/**
> + * __pm_runtime_put_autosuspend - Drop device usage counter and queue autosuspend if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, queue up a work item for @dev like in pm_request_autosuspend().
> + */
> +static inline int __pm_runtime_put_autosuspend(struct device *dev)
> +{
> + return __pm_runtime_suspend(dev, RPM_GET_PUT | RPM_ASYNC | RPM_AUTO);
> +}
> +
> /**
> * pm_runtime_put_autosuspend - Drop device usage counter and queue autosuspend if 0.
> * @dev: Target device.

--
Regards,

Laurent Pinchart