windfarm_cpufreq_clamp.c

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#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/cpufreq.h>

#include <asm/prom.h>

#include "windfarm.h"

#define VERSION "0.3"

static int clamped;
static struct wf_control *clamp_control;

static int clamp_notifier_call(struct notifier_block *self,
                   unsigned long event, void *data)
{
    struct cpufreq_policy *p = data;
    unsigned long max_freq;

    if (event != CPUFREQ_ADJUST)
        return 0;

    max_freq = clamped ? (p->cpuinfo.min_freq) : (p->cpuinfo.max_freq);
    cpufreq_verify_within_limits(p, 0, max_freq);

    return 0;
}

static struct notifier_block clamp_notifier = {
    .notifier_call = clamp_notifier_call,
};

static int clamp_set(struct wf_control *ct, s32 value)
{
    if (value)
        printk(KERN_INFO "windfarm: Clamping CPU frequency to "
               "minimum !\n");
    else
        printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
    clamped = value;
    cpufreq_update_policy(0);
    return 0;
}

static int clamp_get(struct wf_control *ct, s32 *value)
{
    *value = clamped;
    return 0;
}

static s32 clamp_min(struct wf_control *ct)
{
    return 0;
}

static s32 clamp_max(struct wf_control *ct)
{
    return 1;
}

static struct wf_control_ops clamp_ops = {
    .set_value  = clamp_set,
    .get_value  = clamp_get,
    .get_min    = clamp_min,
    .get_max    = clamp_max,
    .owner      = THIS_MODULE,
};

static int __init wf_cpufreq_clamp_init(void)
{
    struct wf_control *clamp;

    clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
    if (clamp == NULL)
        return -ENOMEM;
    cpufreq_register_notifier(&clamp_notifier, CPUFREQ_POLICY_NOTIFIER);
    clamp->ops = &clamp_ops;
    clamp->name = "cpufreq-clamp";
    if (wf_register_control(clamp))
        goto fail;
    clamp_control = clamp;
    return 0;
 fail:
    kfree(clamp);
    return -ENODEV;
}

static void __exit wf_cpufreq_clamp_exit(void)
{
    if (clamp_control)
        wf_unregister_control(clamp_control);
}


module_init(wf_cpufreq_clamp_init);
module_exit(wf_cpufreq_clamp_exit);

MODULE_AUTHOR("Benjamin Herrenschmidt <[email protected]>");
MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
MODULE_LICENSE("GPL");