linux/arch/powerpc/platforms/cell/cpufreq_spudemand.c
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   1/*
   2 * spu aware cpufreq governor for the cell processor
   3 *
   4 * \xC2\xA9 Copyright IBM Corporation 2006-2008
   5 *
   6 * Author: Christian Krafft <krafft@de.ibm.com>
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License as published by
  10 * the Free Software Foundation; either version 2, or (at your option)
  11 * any later version.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program; if not, write to the Free Software
  20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23#include <linux/cpufreq.h>
  24#include <linux/sched.h>
  25#include <linux/module.h>
  26#include <linux/timer.h>
  27#include <linux/workqueue.h>
  28#include <linux/atomic.h>
  29#include <asm/machdep.h>
  30#include <asm/spu.h>
  31
  32#define POLL_TIME       100000          /* in \xC2\xB5s */
  33#define EXP             753             /* exp(-1) in fixed-point */
  34
  35struct spu_gov_info_struct {
  36        unsigned long busy_spus;        /* fixed-point */
  37        struct cpufreq_policy *policy;
  38        struct delayed_work work;
  39        unsigned int poll_int;          /* \xC2\xB5s */
  40};
  41static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  42
  43static int calc_freq(struct spu_gov_info_struct *info)
  44{
  45        int cpu;
  46        int busy_spus;
  47
  48        cpu = info->policy->cpu;
  49        busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
  50
  51        CALC_LOAD(info->busy_spus, EXP, busy_spus * FIXED_1);
  52        pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
  53                        cpu, busy_spus, info->busy_spus);
  54
  55        return info->policy->max * info->busy_spus / FIXED_1;
  56}
  57
  58static void spu_gov_work(struct work_struct *work)
  59{
  60        struct spu_gov_info_struct *info;
  61        int delay;
  62        unsigned long target_freq;
  63
  64        info = container_of(work, struct spu_gov_info_struct, work.work);
  65
  66        /* after cancel_delayed_work_sync we unset info->policy */
  67        BUG_ON(info->policy == NULL);
  68
  69        target_freq = calc_freq(info);
  70        __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
  71
  72        delay = usecs_to_jiffies(info->poll_int);
  73        schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  74}
  75
  76static void spu_gov_init_work(struct spu_gov_info_struct *info)
  77{
  78        int delay = usecs_to_jiffies(info->poll_int);
  79        INIT_DELAYED_WORK_DEFERRABLE(&info->work, spu_gov_work);
  80        schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  81}
  82
  83static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
  84{
  85        cancel_delayed_work_sync(&info->work);
  86}
  87
  88static int spu_gov_govern(struct cpufreq_policy *policy, unsigned int event)
  89{
  90        unsigned int cpu = policy->cpu;
  91        struct spu_gov_info_struct *info, *affected_info;
  92        int i;
  93        int ret = 0;
  94
  95        info = &per_cpu(spu_gov_info, cpu);
  96
  97        switch (event) {
  98        case CPUFREQ_GOV_START:
  99                if (!cpu_online(cpu)) {
 100                        printk(KERN_ERR "cpu %d is not online\n", cpu);
 101                        ret = -EINVAL;
 102                        break;
 103                }
 104
 105                if (!policy->cur) {
 106                        printk(KERN_ERR "no cpu specified in policy\n");
 107                        ret = -EINVAL;
 108                        break;
 109                }
 110
 111                /* initialize spu_gov_info for all affected cpus */
 112                for_each_cpu(i, policy->cpus) {
 113                        affected_info = &per_cpu(spu_gov_info, i);
 114                        affected_info->policy = policy;
 115                }
 116
 117                info->poll_int = POLL_TIME;
 118
 119                /* setup timer */
 120                spu_gov_init_work(info);
 121
 122                break;
 123
 124        case CPUFREQ_GOV_STOP:
 125                /* cancel timer */
 126                spu_gov_cancel_work(info);
 127
 128                /* clean spu_gov_info for all affected cpus */
 129                for_each_cpu (i, policy->cpus) {
 130                        info = &per_cpu(spu_gov_info, i);
 131                        info->policy = NULL;
 132                }
 133
 134                break;
 135        }
 136
 137        return ret;
 138}
 139
 140static struct cpufreq_governor spu_governor = {
 141        .name = "spudemand",
 142        .governor = spu_gov_govern,
 143        .owner = THIS_MODULE,
 144};
 145
 146/*
 147 * module init and destoy
 148 */
 149
 150static int __init spu_gov_init(void)
 151{
 152        int ret;
 153
 154        ret = cpufreq_register_governor(&spu_governor);
 155        if (ret)
 156                printk(KERN_ERR "registration of governor failed\n");
 157        return ret;
 158}
 159
 160static void __exit spu_gov_exit(void)
 161{
 162        cpufreq_unregister_governor(&spu_governor);
 163}
 164
 165
 166module_init(spu_gov_init);
 167module_exit(spu_gov_exit);
 168
 169MODULE_LICENSE("GPL");
 170MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 171
 172