linux-kernel - Re: [PATCH v2] PM / Runtime: Only force-resume device if it has been force-suspended

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Date:	Thu, 21 Apr 2016 21:52:56 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Kevin Hilman <khilman@...nel.org>,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] PM / Runtime: Only force-resume device if it has been force-suspended

On Thursday, April 21, 2016 02:52:55 AM Laurent Pinchart wrote:
> The pm_runtime_force_suspend() and pm_runtime_force_resume() helpers are
> designed to help driver being RPM-centric by offering an easy way to
> manage runtime PM state during system suspend and resume. The first
> function will force the device into runtime suspend at system suspend
> time, while the second one will perform the reverse operation at system
> resume time.
> 
> However, the pm_runtime_force_resume() really forces resume, regardless
> of whether the device was running or already suspended before the call
> to pm_runtime_force_suspend(). This results in devices being runtime
> resumed at system resume time when they shouldn't.
> 
> Fix this by recording whether the device has been forcefully suspended
> in pm_runtime_force_suspend() and condition resume in
> pm_runtime_force_resume() to that state.
> 
> All current users of pm_runtime_force_resume() call the function
> unconditionally in their system resume handler (some actually set it as
> the resume handler), all after calling pm_runtime_force_suspend() at
> system suspend time. The change in behaviour should thus be safe.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
> Reviewed-by: Kevin Hilman <khilman@...libre.com>

Ulf, any comments?

> ---
>  drivers/base/power/runtime.c | 19 ++++++++++++++++---
>  include/linux/pm.h           |  1 +
>  2 files changed, 17 insertions(+), 3 deletions(-)
> 
> Changes since v1:
> 
> - Fix typos
> - Protect the is_force_suspended flag modifications with power.lock
> 
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 4c7055009bd6..8fc7fba811fa 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1400,6 +1400,7 @@ void pm_runtime_init(struct device *dev)
>  	pm_suspend_ignore_children(dev, false);
>  	dev->power.runtime_auto = true;
>  
> +	dev->power.is_force_suspended = false;
>  	dev->power.request_pending = false;
>  	dev->power.request = RPM_REQ_NONE;
>  	dev->power.deferred_resume = false;
> @@ -1457,6 +1458,7 @@ void pm_runtime_remove(struct device *dev)
>  int pm_runtime_force_suspend(struct device *dev)
>  {
>  	int (*callback)(struct device *);
> +	unsigned long flags;
>  	int ret = 0;
>  
>  	pm_runtime_disable(dev);
> @@ -1475,6 +1477,10 @@ int pm_runtime_force_suspend(struct device *dev)
>  		goto err;
>  
>  	pm_runtime_set_suspended(dev);
> +	spin_lock_irqsave(&dev->power.lock, flags);
> +	dev->power.is_force_suspended = true;
> +	spin_unlock_irqrestore(&dev->power.lock, flags);
> +
>  	return 0;
>  err:
>  	pm_runtime_enable(dev);
> @@ -1483,13 +1489,13 @@ err:
>  EXPORT_SYMBOL_GPL(pm_runtime_force_suspend);
>  
>  /**
> - * pm_runtime_force_resume - Force a device into resume state.
> + * pm_runtime_force_resume - Force a device into resume state if needed.
>   * @dev: Device to resume.
>   *
>   * Prior invoking this function we expect the user to have brought the device
>   * into low power state by a call to pm_runtime_force_suspend(). Here we reverse
> - * those actions and brings the device into full power. We update the runtime PM
> - * status and re-enables runtime PM.
> + * those actions and bring the device back to its runtime PM state before forced
> + * suspension. We update the runtime PM status and re-enable runtime PM.
>   *
>   * Typically this function may be invoked from a system resume callback to make
>   * sure the device is put into full power state.
> @@ -1497,8 +1503,12 @@ EXPORT_SYMBOL_GPL(pm_runtime_force_suspend);
>  int pm_runtime_force_resume(struct device *dev)
>  {
>  	int (*callback)(struct device *);
> +	unsigned long flags;
>  	int ret = 0;
>  
> +	if (!dev->power.is_force_suspended)
> +		goto out;
> +
>  	callback = RPM_GET_CALLBACK(dev, runtime_resume);
>  
>  	if (!callback) {
> @@ -1510,6 +1520,9 @@ int pm_runtime_force_resume(struct device *dev)
>  	if (ret)
>  		goto out;
>  
> +	spin_lock_irqsave(&dev->power.lock, flags);
> +	dev->power.is_force_suspended = false;
> +	spin_unlock_irqrestore(&dev->power.lock, flags);
>  	pm_runtime_set_active(dev);
>  	pm_runtime_mark_last_busy(dev);
>  out:
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 6a5d654f4447..bec15e0f244e 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -596,6 +596,7 @@ struct dev_pm_info {
>  	unsigned int		use_autosuspend:1;
>  	unsigned int		timer_autosuspends:1;
>  	unsigned int		memalloc_noio:1;
> +	unsigned int		is_force_suspended:1;
>  	enum rpm_request	request;
>  	enum rpm_status		runtime_status;
>  	int			runtime_error;
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.