cpufreq_spudemand.c

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/*
 * spu aware cpufreq governor for the cell processor
 *
 * © Copyright IBM Corporation 2006-2008
 *
 * Author: Christian Krafft <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/cpufreq.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/atomic.h>
#include <asm/machdep.h>
#include <asm/spu.h>

#define POLL_TIME   100000      /* in µs */
#define EXP     753     /* exp(-1) in fixed-point */

struct spu_gov_info_struct {
    unsigned long busy_spus;    /* fixed-point */
    struct cpufreq_policy *policy;
    struct delayed_work work;
    unsigned int poll_int;      /* µs */
};
static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);

static int calc_freq(struct spu_gov_info_struct *info)
{
    int cpu;
    int busy_spus;

    cpu = info->policy->cpu;
    busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);

    CALC_LOAD(info->busy_spus, EXP, busy_spus * FIXED_1);
    pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
            cpu, busy_spus, info->busy_spus);

    return info->policy->max * info->busy_spus / FIXED_1;
}

static void spu_gov_work(struct work_struct *work)
{
    struct spu_gov_info_struct *info;
    int delay;
    unsigned long target_freq;

    info = container_of(work, struct spu_gov_info_struct, work.work);

    /* after cancel_delayed_work_sync we unset info->policy */
    BUG_ON(info->policy == NULL);

    target_freq = calc_freq(info);
    __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);

    delay = usecs_to_jiffies(info->poll_int);
    schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
}

static void spu_gov_init_work(struct spu_gov_info_struct *info)
{
    int delay = usecs_to_jiffies(info->poll_int);
    INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
    schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
}

static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
{
    cancel_delayed_work_sync(&info->work);
}

static int spu_gov_govern(struct cpufreq_policy *policy, unsigned int event)
{
    unsigned int cpu = policy->cpu;
    struct spu_gov_info_struct *info, *affected_info;
    int i;
    int ret = 0;

    info = &per_cpu(spu_gov_info, cpu);

    switch (event) {
    case CPUFREQ_GOV_START:
        if (!cpu_online(cpu)) {
            printk(KERN_ERR "cpu %d is not online\n", cpu);
            ret = -EINVAL;
            break;
        }

        if (!policy->cur) {
            printk(KERN_ERR "no cpu specified in policy\n");
            ret = -EINVAL;
            break;
        }

        /* initialize spu_gov_info for all affected cpus */
        for_each_cpu(i, policy->cpus) {
            affected_info = &per_cpu(spu_gov_info, i);
            affected_info->policy = policy;
        }

        info->poll_int = POLL_TIME;

        /* setup timer */
        spu_gov_init_work(info);

        break;

    case CPUFREQ_GOV_STOP:
        /* cancel timer */
        spu_gov_cancel_work(info);

        /* clean spu_gov_info for all affected cpus */
        for_each_cpu (i, policy->cpus) {
            info = &per_cpu(spu_gov_info, i);
            info->policy = NULL;
        }

        break;
    }

    return ret;
}

static struct cpufreq_governor spu_governor = {
    .name = "spudemand",
    .governor = spu_gov_govern,
    .owner = THIS_MODULE,
};

/*
 * module init and destoy
 */

static int __init spu_gov_init(void)
{
    int ret;

    ret = cpufreq_register_governor(&spu_governor);
    if (ret)
        printk(KERN_ERR "registration of governor failed\n");
    return ret;
}

static void __exit spu_gov_exit(void)
{
    cpufreq_unregister_governor(&spu_governor);
}


module_init(spu_gov_init);
module_exit(spu_gov_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Christian Krafft <[email protected]>");