linux-kernel - Re: [PATCH v7 3/3] PM / wakeup: Show wakeup sources stats in sysfs

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Date:   Tue, 6 Aug 2019 23:32:27 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Tri Vo <trong@...roid.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>
Subject: Re: [PATCH v7 3/3] PM / wakeup: Show wakeup sources stats in sysfs

On Tue, Aug 6, 2019 at 8:51 PM Tri Vo <trong@...roid.com> wrote:
>
> On Mon, Aug 5, 2019 at 4:29 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > Quoting Tri Vo (2019-08-05 10:58:48)
> > > diff --git a/drivers/base/power/wakeup_stats.c b/drivers/base/power/wakeup_stats.c
> > > new file mode 100644
> > > index 000000000000..3a4f55028e27
> > > --- /dev/null
> > > +++ b/drivers/base/power/wakeup_stats.c
> > > @@ -0,0 +1,161 @@
> > [...]
> > > +/**
> > > + * wakeup_source_sysfs_add - Add wakeup_source attributes to sysfs.
> > > + * @parent: Device given wakeup source is associated with (or NULL if virtual).
> > > + * @ws: Wakeup source to be added in sysfs.
> > > + */
> > > +int wakeup_source_sysfs_add(struct device *parent, struct wakeup_source *ws)
> > > +{
> > > +       struct device *dev;
> > > +
> > > +       dev = device_create_with_groups(wakeup_class, parent, MKDEV(0, 0), ws,
> > > +                                       wakeup_source_groups, "wakeup%d",
> > > +                                       ws->id);
> > > +       if (IS_ERR(dev))
> > > +               return PTR_ERR(dev);
> > > +       ws->dev = dev;
> > > +       pm_runtime_no_callbacks(ws->dev);
> >
> > Does this only avoid adding runtime PM attributes?
> >
> > I thought we would call device_set_pm_not_required() on the device here.
> > Probably requiring a bit of copy/paste from device_create_with_groups()
> > so that it can be set before the device is registered. Or another
> > version of device_create_with_groups() that does everything besides call
> > device_add().
>
> Comments on pm_runtime_no_callbacks() say,
>   "Set the power.no_callbacks flag, which tells the PM core that this
>    device is power-managed through its parent and has no runtime PM
>    callbacks of its own.  The runtime sysfs attributes will be removed."
>
> Sound like it's appropriate to apply this function to the wakeup source.

This is only useful if you ever enable PM-runtime for this device.
Which you won't do.

You could use device_set_pm_not_required(), though.