linux-kernel - Re: [PATCH] cpufreq: Allow accessing freq

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Date:	Wed, 8 Jul 2015 10:01:44 +0100
From:	Javi Merino <javi.merino@....com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"rui.zhang@...el.com" <rui.zhang@...el.com>,
	"edubezval@...il.com" <edubezval@...il.com>,
	Pi-Cheng Chen <pi-cheng.chen@...aro.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: Allow accessing freq_table for offline CPUs

Hi Viresh,

one minor nit below

On Wed, Jul 08, 2015 at 08:38:15AM +0100, Viresh Kumar wrote:
> Users of freq table may want to access it for any CPU from
> policy->related_cpus mask. One such user is cpu-cooling layer. It gets a
> list of 'clip_cpus' (equivalent to policy->related_cpus) during
> registration and tries to get freq_table for the first CPU of this mask.
> 
> If the CPU, for which it tries to fetch freq_table, is offline,
> cpufreq_frequency_get_table() fails. This happens because it relies on
> cpufreq_cpu_get_raw() for its functioning which returns policy only for
> online CPUs.
> 
> Fix this by considering offline CPUs, but with a restriction that the
> policy is active at that time.
> 
> Because we will be using 'cpufreq_cpu_data' now, which is internal to
> cpufreq-core, lets also move cpufreq_frequency_get_table() to cpufreq.c
> file.
> 
> Reported-by: Pi-Cheng Chen <pi-cheng.chen@...aro.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> This was recently tried by Pi cheng but in a completely different way:
> http://marc.info/?l=linux-pm&m=143572367402758&w=2
> 
> Its not broken by any stuff in 4.2, but would be good if we can push
> this for 4.2 as well.
> 
>  drivers/cpufreq/cpufreq.c    | 9 +++++++++
>  drivers/cpufreq/freq_table.c | 7 -------
>  2 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 2c22e3902e72..26063afb3eba 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -169,6 +169,15 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy)
>  }
>  EXPORT_SYMBOL_GPL(get_governor_parent_kobj);
>  
> +struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu)
> +{
> +	struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
> +
> +	return policy && !policy_is_inactive(policy) ?
> +		policy->freq_table : NULL;
> +}
> +EXPORT_SYMBOL_GPL(cpufreq_frequency_get_table);
> +
>  static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
>  {
>  	u64 idle_time;
> diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
> index df14766a8e06..7551f01e8536 100644
> --- a/drivers/cpufreq/freq_table.c
> +++ b/drivers/cpufreq/freq_table.c
> @@ -299,13 +299,6 @@ EXPORT_SYMBOL_GPL(cpufreq_table_validate_and_show);
>  
>  struct cpufreq_policy *cpufreq_cpu_get_raw(unsigned int cpu);

While you are at it, you can remove this prototype of
cpufreq_cpu_get_raw(), as it's no longer needed.

Cheers,
Javi

>  
> -struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu)
> -{
> -	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
> -	return policy ? policy->freq_table : NULL;
> -}
> -EXPORT_SYMBOL_GPL(cpufreq_frequency_get_table);
> -
>  MODULE_AUTHOR("Dominik Brodowski <linux@...do.de>");
>  MODULE_DESCRIPTION("CPUfreq frequency table helpers");
>  MODULE_LICENSE("GPL");
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