linux-kernel - Re: [PATCH 3/7] PM / Domain: Add struct device to genpd

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Date:   Thu, 22 Mar 2018 17:59:03 +0800
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Kevin Hilman <khilman@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Linux PM <linux-pm@...r.kernel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Nishanth Menon <nm@...com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] PM / Domain: Add struct device to genpd

On 22-03-18, 10:30, Ulf Hansson wrote:
> On 22 December 2017 at 08:26, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > The power-domain core would be using the OPP core going forward and the
> > OPP core has the basic requirement of a device structure for its working.
> 
> According to the OPP core also seems to require the ->dev.of_node to
> be set. Actually, it seems like that part belongs in patch4 instead,
> while starting to make use of the opp OF APIs. Could you please move
> it?

You meaning setting of the of_node to the next patch? I can do that if that;s
what you want.

> > +static struct bus_type genpd_bus_type = {
> > +       .name =         "genpd",
> > +};
> 
> This seems silly. Can't we just avoid having a bus type altogether,
> thus no need to call bus_register() as well?

I thought we need a bus where we want to add the device, haven't tried with that
pointer being empty. Will try that and let you know.

> > +
> >  /**
> >   * pm_genpd_init - Initialize a generic I/O PM domain object.
> >   * @genpd: PM domain object to initialize.
> > @@ -1687,6 +1691,18 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
> >                         return ret;
> >         }
> >
> > +       genpd->dev.bus = &genpd_bus_type;
> > +       device_initialize(&genpd->dev);
> > +       dev_set_name(&genpd->dev, "%s", genpd->name);
> > +
> > +       ret = device_add(&genpd->dev);
> 
> What's the point of adding the device? Can we skip this step, as I
> guess the opp core is only using the device as cookie rather actual
> using it? No?

We also use it for the OPP debugfs stuff, so that would be required I believe.
We also use it for playing with clk/regulator stuff as well, though we may not
use it in genpd case for now.

-- 
viresh