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cpufreq: governor: Ensure sufficiently large sampling intervals 

After commit aa7519af45 (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: aa7519af45 (cpufreq: Use transition_delay_us for legacy governors as well)
Reported-by: Andy Tang <andy.tang@nxp.com>
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Andy Tang <andy.tang@nxp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Rafael J. Wysocki 2017-12-18 02:15:32 +01:00
parent ccc153a6de
commit 56026645e2
1 changed files with 16 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/cpufreq/cpufreq_governor.c
View File

@ -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;