Date:	Thu, 21 Apr 2016 23:57:58 +0300
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Ulf Hansson <ulf.hansson@...aro.org>, 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

Hi Rafael,

On Thursday 21 Apr 2016 21:52:56 Rafael J. Wysocki wrote:
> 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?

Ulf has proposed a different approach in "[PATCH] PM / Runtime: Defer resuming 
of the device in pm_runtime_force_resume()". I agree that using usage_count is 
better than introducing a new state flag in struct dev_pm_info, with a caveat: 
it doesn't work properly :-). We would have to fix genpd first, as commented 
in a reply to Ulf's patch.

> > ---
> > 
> >  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;

-- 
Regards,

Laurent Pinchart

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