linux-kernel - Re: [PATCH] cpufreq: skip loading acpi_cpufreq after intel

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Message-ID: <CAKohpokdyk9hfBreVeXttN23biTVjWiJRm8eYkfAjLz+cbnreQ@mail.gmail.com>
Date:	Fri, 20 Sep 2013 11:40:18 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: skip loading acpi_cpufreq after intel_pstate

On 20 September 2013 10:56, Yinghai Lu <yinghai@...nel.org> wrote:
> If the hw support intel_pstate and acpi_cpufreq, intel_pstate will
> get loaded at first.

s/at //

>
> acpi_cpufreq_init will call acpi_cpufreq_early_init()
> and it allocate perf data and init those perf data in ACPI core, (that

s/it /that will /

> will go over all cpus).

s/go over/cover/

> but late it will free them as cpufreq_register_driver(acpi_cpufreq) will

s/late/later

> return fail as init_pstate already take over before.

write it as: fail as intel_pstate is already registered.

> Use cpufreq_get_current_driver() to check if we can skip the
> acpi_cpufreq loading.

The below material looks to be a separate issue and so we
probably break this patch into two?

> Also there is racing in
>         __acpi_processor_start
>                  ==> acpi_processor_load_module
>                          ==> request_module_nowait/requested = 1

> Index: linux-2.6/drivers/cpufreq/acpi-cpufreq.c
> ===================================================================
> --- linux-2.6.orig/drivers/cpufreq/acpi-cpufreq.c
> +++ linux-2.6/drivers/cpufreq/acpi-cpufreq.c
> @@ -986,6 +986,10 @@ static int __init acpi_cpufreq_init(void
>  {
>         int ret;
>
> +       /* don't keep reloading if cpufreq_driver exists */
> +       if (cpufreq_get_current_driver())
> +               return 0;
> +
>         if (acpi_disabled)
>                 return 0;

This looks fine to me..

> Index: linux-2.6/drivers/acpi/processor_perflib.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/processor_perflib.c
> +++ linux-2.6/drivers/acpi/processor_perflib.c

Can't really review this one.. Rafael will do it..
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