linux-kernel - Re: [PATCH v6 3/8] cpufreq:acpi:x86: Adjust the acpi-cpufreq.c code to work with common boost solution

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Date:	Fri, 26 Jul 2013 10:09:40 +0200
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <eduardo.valentin@...com>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Myungjoo Ham <myungjoo.ham@...sung.com>, durgadoss.r@...el.com
Subject: Re: [PATCH v6 3/8] cpufreq:acpi:x86: Adjust the acpi-cpufreq.c code to
 work with common boost solution

On Fri, 26 Jul 2013 12:58:02 +0530 Viresh Kumar wrote,
> On 25 July 2013 22:03, Lukasz Majewski <l.majewski@...sung.com> wrote:
> > diff --git a/drivers/cpufreq/acpi-cpufreq.c
> > b/drivers/cpufreq/acpi-cpufreq.c
> 
> >  static void __init acpi_cpufreq_boost_init(void)
> >  {
> > +       acpi_cpufreq_driver.boost_supported = false;
	    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ [*]
> 
> Would be better if we do this in else of below if.

We need to set boost_supported = false at [*] for the case when:
1. msrs_alloc fails 
or 
2. acpi_cpufreq is built as a module and can be inserted and removed
several times. Without [*] we could end up with wrong (not false)
initial state.

> 
> >         if (boot_cpu_has(X86_FEATURE_CPB) ||
> > boot_cpu_has(X86_FEATURE_IDA)) { msrs = msrs_alloc();
> 
> 
> > @@ -1021,12 +995,11 @@ static int __init acpi_cpufreq_init(void)
> >                         *iter = &cpb;
> >         }
> >  #endif
> > +       acpi_cpufreq_boost_init();
	    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ [**]
> 
> We are calling it before registering cpufreq driver. Will this have
> any complications?

When we call [**] after the cpufreq_register_driver [***] we end up with
sysfs boost attribute not exported at x86.
The boost attribute is exported at [***] only when
acpi_cpufreq.boost_supported = true. However support for boost at x86
is evaluated at acpi_cpufreq_boost_init().


> 
> >         ret = cpufreq_register_driver(&acpi_cpufreq_driver);
> >         if (ret)
> >                 free_acpi_perf_data();
> > -       else
> > -               acpi_cpufreq_boost_init();
> >
> >         return ret;



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
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