linux-kernel - Re: [PATCH] acpi-cpufreq: Skip initialization if a cpufreq driver exists

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Message-ID: <CAOh2x==tXk2Lt_f14_azHNYG2mZzMb9-1b2YUVj=+i=-JLemdg@mail.gmail.com>
Date:   Mon, 7 Jun 2021 12:55:58 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Takashi Iwai <tiwai@...e.de>
Cc:     Kyle Meyer <kyle.meyer@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH] acpi-cpufreq: Skip initialization if a cpufreq driver exists

Hi Rafael,

On Mon, May 24, 2021 at 7:47 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
> On Sat, May 22, 2021 at 12:19 AM Kyle Meyer <kyle.meyer@....com> wrote:

> > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> > index 7e7450453714..e79a945369d1 100644
> > --- a/drivers/cpufreq/acpi-cpufreq.c
> > +++ b/drivers/cpufreq/acpi-cpufreq.c
> > @@ -1003,7 +1003,7 @@ static int __init acpi_cpufreq_init(void)
> >
> >         /* don't keep reloading if cpufreq_driver exists */
> >         if (cpufreq_get_current_driver())
> > -               return -EEXIST;
> > +               return 0;
> >
> >         pr_debug("%s\n", __func__);
> >
> > --
>
> Applied as 5.14 material with some edits in the subject and changelog, thanks!

I am not sure how this is supposed to work. If we return 0 from
acpi_cpufreq_init(),
then the driver will never be used, since it's acpi_cpufreq_init()
will never get
called again later.

cpufreq drivers don't follow the generic device/driver model where a driver gets
probed again if a device appears and so this is broken.

Please revert this patch.