linux-kernel - Re: [PATCH v4 2/7] cpufreq: Add boost frequency support in core

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Date:	Wed, 17 Jul 2013 13:28:29 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lukasz Majewski <l.majewski@...ess.pl>,
	Dirk Brandewie <dirk.brandewie@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Lukasz Majewski <l.majewski@...sung.com>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	Myungjoo Ham <myungjoo.ham@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andre Przywara <andre.przywara@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <eduardo.valentin@...com>
Subject: Re: [PATCH v4 2/7] cpufreq: Add boost frequency support in core

On 20 June 2013 03:55, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Wednesday, June 19, 2013 10:31:02 PM Lukasz Majewski wrote:
>> On Wed, 19 Jun 2013 10:48:53 -0700
>> Dirk Brandewie <dirk.brandewie@...il.com> wrote:
>>
>> > On 06/19/2013 10:12 AM, Lukasz Majewski wrote:

>> > > @@ -1936,6 +2019,16 @@ int cpufreq_register_driver(struct
>> > > + if (!cpufreq_driver->boost_supported)
>> > > +         boost.attr.mode = 0444;
>> > > +
>> > > + ret = cpufreq_sysfs_create_file(&(boost.attr));
>> > > + if (ret) {
>> > > +         pr_err("%s: cannot register global boost sysfs
>> > > file\n",
>> > > +                __func__);
>> > > +         goto err_null_driver;
>> > > + }
>> > > +
>> >
>> > I do not think the boost sysfs should be created at all if boost is
>> > not supported.
>>
>> This was my first thought. But unfortunately this "boost" attribute is
>> always exported at acpi-cpufreq.c and in my opinion is part of a
>> legacy API.
>>
>> I totally agree with the idea of exporting boost only when supported,
>> but I would like to know the community opinion about this (especially
>> Viresh and Rafael shall speak up).
>
> Simple: Export it only when supported.

Guys,

I got confused here. We originally decided to keep this feature as is
for acpi-cpufreq.

So, For acpi-cpufreq:
- when boost isn't supported: create sysfs boost with ro permissions
- when boost is supported: create sysfs boost with rw permissions

So, For others:
- create sysfs boost with rw permissions only when boost is supported

.

Do you want something else? or do you want to change behavior of
acpi-cpufreq driver? I don't why it was designed this way and what
applications use it.
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