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SubjectRe: [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@samsung.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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