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cpufreq_spudemand.c

/*
 * spu aware cpufreq governor for the cell processor
 *
 * © Copyright IBM Corporation 2006-2008
 *
 * Author: Christian Krafft <krafft@de.ibm.com>
 *
 * 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/timer.h>
#include <linux/workqueue.h>
#include <asm/atomic.h>
#include <asm/machdep.h>
#include <asm/spu.h>

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

00034 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 struct workqueue_struct *kspugov_wq;

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);
      queue_delayed_work_on(info->policy->cpu, kspugov_wq, &info->work, delay);
}

static void spu_gov_init_work(struct spu_gov_info_struct *info)
{
      int delay = usecs_to_jiffies(info->poll_int);
      INIT_DELAYED_WORK_DEFERRABLE(&info->work, spu_gov_work);
      queue_delayed_work_on(info->policy->cpu, kspugov_wq, &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_mask(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_mask (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;

      kspugov_wq = create_workqueue("kspugov");
      if (!kspugov_wq) {
            printk(KERN_ERR "creation of kspugov failed\n");
            ret = -EFAULT;
            goto out;
      }

      ret = cpufreq_register_governor(&spu_governor);
      if (ret) {
            printk(KERN_ERR "registration of governor failed\n");
            destroy_workqueue(kspugov_wq);
            goto out;
      }
out:
      return ret;
}

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


module_init(spu_gov_init);
module_exit(spu_gov_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");


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