linux-kernel - Re: [PATCH update] PM: Introduce core framework for run-time PM of I/O devices (rev. 15)

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Message-Id: <200908122213.14174.rjw@sisk.pl>
Date:	Wed, 12 Aug 2009 22:13:14 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>, Greg KH <gregkh@...e.de>,
	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH update] PM: Introduce core framework for run-time PM of I/O devices (rev. 15)

On Wednesday 12 August 2009, Magnus Damm wrote:
> Hi Rafael,

Hi,

> On Mon, Aug 10, 2009 at 6:13 AM, Rafael J. Wysocki<rjw@...k.pl> wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > Subject: PM: Introduce core framework for run-time PM of I/O devices (rev. 15)
> >
> > Introduce a core framework for run-time power management of I/O
> > devices.  Add device run-time PM fields to 'struct dev_pm_info'
> > and device run-time PM callbacks to 'struct dev_pm_ops'.  Introduce
> > a run-time PM workqueue and define some device run-time PM helper
> > functions at the core level.  Document all these things.
> >
> > Special thanks to Alan Stern for his help with the design and
> > multiple detailed reviews of the pereceding versions of this patch
> > and to Magnus Damm for testing feedback.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> 
> Looking good! I have a few nitpicks below, but from a functional
> perspective it's all good. I've tested v15 with platform device
> drivers for I2C, UIO and framebuffer. Before adding my "Acked-by"  I
> also want to test the V4L capture driver, but I need to wait a few
> days until I can get my hands on such a hardware platform.
> 
> Thanks for folding in and fixing up the debug patch. I was able to
> drop most remaining patches thanks to feedback from Alan. So the only
> needed patch apart from this one (and the ones in your linux-next
> branch) is the one in this micro-series: "PM: Runtime PM v15 for
> Platform Devices 20090812".
> 
> > --- linux-2.6.orig/include/linux/pm.h
> > +++ linux-2.6/include/linux/pm.h
> [..]
> >  struct dev_pm_info {
> >        pm_message_t            power_state;
> > -       unsigned                can_wakeup:1;
> > -       unsigned                should_wakeup:1;
> > +       unsigned int            can_wakeup:1;
> > +       unsigned int            should_wakeup:1;
> >        enum dpm_state          status;         /* Owned by the PM core */
> > -#ifdef CONFIG_PM_SLEEP
> > +#ifdef CONFIG_PM_SLEEP
> >        struct list_head        entry;
> >  #endif
> > +#ifdef CONFIG_PM_RUNTIME
> > +       struct timer_list       suspend_timer;
> > +       unsigned long           timer_expires;
> > +       struct work_struct      work;
> > +       wait_queue_head_t       wait_queue;
> > +       spinlock_t              lock;
> > +       atomic_t                usage_count;
> > +       atomic_t                child_count;
> 
> I suppose child_count has to be atomic?

I'd say so, it's modified in a few places without locking.

> > --- /dev/null
> > +++ linux-2.6/drivers/base/power/runtime.c
> [...]
> > +int __pm_runtime_suspend(struct device *dev, bool from_wq)
> > +       __releases(&dev->power.lock) __acquires(&dev->power.lock)
> [...]
> > +       if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_suspend) {
> > +               spin_unlock_irq(&dev->power.lock);
> > +
> > +               retval = dev->bus->pm->runtime_suspend(dev);
> > +
> > +               spin_lock_irq(&dev->power.lock);
> > +               dev->power.runtime_error = retval;
> > +       } else {
> > +               retval = -ENOSYS;
> > +       }
> 
> Nit: { and } above do not follow the regular coding style.

Well, you've got a very good answer to this from Alan. ;-)

Thanks,
Rafael
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