linux-imx

/*

 * drivers/cpufreq/cpufreq_governor.c

 *

 * CPUFREQ governors common code

 *

 * Copyright    (C) 2001 Russell King

 *      (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.

 *      (C) 2003 Jun Nakajima <jun.nakajima@intel.com>

 *      (C) 2009 Alexander Clouter <alex@digriz.org.uk>

 *      (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

​

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

​

#include <linux/export.h>

#include <linux/kernel_stat.h>

#include <linux/slab.h>

​

#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);

​

/* Common sysfs tunables */

/**

 * store_sampling_rate - update sampling rate effective immediately if needed.

 *

 * If new rate is smaller than the old, simply updating

 * dbs.sampling_rate might not be appropriate. For example, if the

 * original sampling_rate was 1 second and the requested new sampling rate is 10

 * ms because the user needs immediate reaction from ondemand governor, but not

 * sure if higher frequency will be required or not, then, the governor may

 * change the sampling rate too late; up to 1 second later. Thus, if we are

 * reducing the sampling rate, we need to make the new value effective

 * immediately.

 *

 * This must be called with dbs_data->mutex held, otherwise traversing

 * policy_dbs_list isn't safe.

 */

ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf,

                size_t count)

{

    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", &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.