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cpufreq: add cpufreq_driver_resolve_freq()

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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@intel.com>
Signed-off-by: Steve Muckle <smuckle@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Steve Muckle 2016-07-13 13:25:25 -07:00 committed by Rafael J. Wysocki
parent da7de91c3e
commit e3c0623608
2 changed files with 41 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

25
drivers/cpufreq/cpufreq.c
View file

@ -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);

16
include/linux/cpufreq.h
View file

@ -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);