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Commit 56026645 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpufreq: governor: Ensure sufficiently large sampling intervals 



After commit aa7519af (cpufreq: Use transition_delay_us for legacy
governors as well) the sampling_rate field of struct dbs_data may be
less than the tick period which causes dbs_update() to produce
incorrect results, so make the code ensure that the value of that
field will always be sufficiently large.

Fixes: aa7519af (cpufreq: Use transition_delay_us for legacy governors as well)
Reported-by: default avatarAndy Tang <andy.tang@nxp.com>
Reported-by: default avatarDoug Smythies <dsmythies@telus.net>
Tested-by: default avatarAndy Tang <andy.tang@nxp.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent ccc153a6

drivers/cpufreq/cpufreq_governor.c

+16 −3
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ 


#include "cpufreq_governor.h"



#define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL	(2 * TICK_NSEC / NSEC_PER_USEC)



static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);



static DEFINE_MUTEX(gov_dbs_data_mutex);
@@ -47,11 +49,15 @@ ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf, 
{

	struct dbs_data *dbs_data = to_dbs_data(attr_set);

	struct policy_dbs_info *policy_dbs;

	unsigned int sampling_interval;

	int ret;

	ret = sscanf(buf, "%u", &dbs_data->sampling_rate);

	if (ret != 1)



	ret = sscanf(buf, "%u", &sampling_interval);

	if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL)

		return -EINVAL;



	dbs_data->sampling_rate = sampling_interval;



	/*

	 * We are operating under dbs_data->mutex and so the list and its

	 * entries can't be freed concurrently.
@@ -430,7 +436,14 @@ int cpufreq_dbs_governor_init(struct cpufreq_policy *policy) 
	if (ret)

		goto free_policy_dbs_info;



	dbs_data->sampling_rate = cpufreq_policy_transition_delay_us(policy);

	/*

	 * The sampling interval should not be less than the transition latency

	 * of the CPU and it also cannot be too small for dbs_update() to work

	 * correctly.

	 */

	dbs_data->sampling_rate = max_t(unsigned int,

					CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,

					cpufreq_policy_transition_delay_us(policy));



	if (!have_governor_per_policy())

		gov->gdbs_data = dbs_data;