linux-kernel - Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve

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Message-ID: <20160721195926.GF3122@ubuntu>
Date:	Thu, 21 Jul 2016 12:59:26 -0700
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Steve Muckle <smuckle@...aro.org>
Subject: Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq()

On 13-07-16, 13:25, Steve Muckle wrote:
> Cpufreq governors may need to know what a particular target frequency
> maps to in the driver without necessarily wanting to set the frequency.
> Support this operation via a new cpufreq API,
> cpufreq_driver_resolve_freq(). This API returns the lowest driver
> frequency equal or greater than the target frequency
> (CPUFREQ_RELATION_L), subject to any policy (min/max) or driver
> limitations. The mapping is also cached in the policy so that a
> subsequent fast_switch operation can avoid repeating the same lookup.
> 
> The API will call a new cpufreq driver callback, resolve_freq(), if it
> has been registered by the driver. Otherwise the frequency is resolved
> via cpufreq_frequency_table_target(). Rather than require ->target()
> style drivers to provide a resolve_freq() callback it is left to the
> caller to ensure that the driver implements this callback if necessary
> to use cpufreq_driver_resolve_freq().
> 
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Steve Muckle <smuckle@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 25 +++++++++++++++++++++++++
>  include/linux/cpufreq.h   | 16 ++++++++++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 118b4f30a406..b696baeb249d 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -492,6 +492,29 @@ void cpufreq_disable_fast_switch(struct cpufreq_policy *policy)
>  }
>  EXPORT_SYMBOL_GPL(cpufreq_disable_fast_switch);
>  
> +/**
> + * cpufreq_driver_resolve_freq - Map a target frequency to a driver-supported
> + * one.
> + * @target_freq: target frequency to resolve.
> + *
> + * The target to driver frequency mapping is cached in the policy.
> + *
> + * Return: Lowest driver-supported frequency greater than or equal to the
> + * given target_freq, subject to policy (min/max) and driver limitations.
> + */
> +unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
> +					 unsigned int target_freq)
> +{
> +	target_freq = clamp_val(target_freq, policy->min, policy->max);
> +	policy->cached_target_freq = target_freq;
> +	if (cpufreq_driver->resolve_freq)
> +		return cpufreq_driver->resolve_freq(policy, target_freq);

Any reason why we still have this call around ? I thought the whole
attempt I made was to get rid of this :)

The core can do this pretty much now by itself, why do we still want
this call?

Also, your series doesn't add a user for it yet, so better drop it for
now.

-- 
viresh