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Commit e3c06236 authored by Steve Muckle's avatar Steve Muckle Committed by Rafael J. Wysocki
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cpufreq: add cpufreq_driver_resolve_freq() 



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: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarSteve Muckle <smuckle@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent da7de91c

drivers/cpufreq/cpufreq.c

+25 −0
Original line number Diff line number Diff line
@@ -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);

	policy->cached_resolved_idx =

		cpufreq_frequency_table_target(policy, target_freq,

					       CPUFREQ_RELATION_L);

	return policy->freq_table[policy->cached_resolved_idx].frequency;

}



/*********************************************************************

 *                          SYSFS INTERFACE                          *

 *********************************************************************/
@@ -2199,6 +2222,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy, 
	policy->min = new_policy->min;

	policy->max = new_policy->max;



	policy->cached_target_freq = UINT_MAX;



	pr_debug("new min and max freqs are %u - %u kHz\n",

		 policy->min, policy->max);

include/linux/cpufreq.h

+16 −0
Original line number Diff line number Diff line
@@ -120,6 +120,10 @@ struct cpufreq_policy { 
	bool			fast_switch_possible;

	bool			fast_switch_enabled;



	 /* Cached frequency lookup from cpufreq_driver_resolve_freq. */

	unsigned int cached_target_freq;

	int cached_resolved_idx;



	/* Synchronization for frequency transitions */

	bool			transition_ongoing; /* Tracks transition status */

	spinlock_t		transition_lock;
@@ -270,6 +274,16 @@ struct cpufreq_driver { 
					unsigned int index);

	unsigned int	(*fast_switch)(struct cpufreq_policy *policy,

				       unsigned int target_freq);



	/*

	 * Caches and returns the lowest driver-supported frequency greater than

	 * or equal to the target frequency, subject to any driver limitations.

	 * Does not set the frequency. Only to be implemented for drivers with

	 * target().

	 */

	unsigned int	(*resolve_freq)(struct cpufreq_policy *policy,

					unsigned int target_freq);



	/*

	 * Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION

	 * unset.
@@ -501,6 +515,8 @@ int cpufreq_driver_target(struct cpufreq_policy *policy, 
int __cpufreq_driver_target(struct cpufreq_policy *policy,

				   unsigned int target_freq,

				   unsigned int relation);

unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,

					 unsigned int target_freq);

int cpufreq_register_governor(struct cpufreq_governor *governor);

void cpufreq_unregister_governor(struct cpufreq_governor *governor);