LXR linux/arch/powerpc/platforms/cell/cpufreq

   1/*
   2 * spu aware cpufreq governor for the cell processor
   3 *
   4 * © 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/sched/loadavg.h>
  26#include <linux/module.h>
  27#include <linux/timer.h>
  28#include <linux/workqueue.h>
  29#include <linux/atomic.h>
  30#include <asm/machdep.h>
  31#include <asm/spu.h>
  32
  33#define POLL_TIME       100000          /* in µs */
  34#define EXP             753             /* exp(-1) in fixed-point */
  35
  36struct spu_gov_info_struct {
  37        unsigned long busy_spus;        /* fixed-point */
  38        struct cpufreq_policy *policy;
  39        struct delayed_work work;
  40        unsigned int poll_int;          /* µs */
  41};
  42static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  43
  44static int calc_freq(struct spu_gov_info_struct *info)
  45{
  46        int cpu;
  47        int busy_spus;
  48
  49        cpu = info->policy->cpu;
  50        busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
  51
  52        CALC_LOAD(info->busy_spus, EXP, busy_spus * FIXED_1);
  53        pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
  54                        cpu, busy_spus, info->busy_spus);
  55
  56        return info->policy->max * info->busy_spus / FIXED_1;
  57}
  58
  59static void spu_gov_work(struct work_struct *work)
  60{
  61        struct spu_gov_info_struct *info;
  62        int delay;
  63        unsigned long target_freq;
  64
  65        info = container_of(work, struct spu_gov_info_struct, work.work);
  66
  67        /* after cancel_delayed_work_sync we unset info->policy */
  68        BUG_ON(info->policy == NULL);
  69
  70        target_freq = calc_freq(info);
  71        __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
  72
  73        delay = usecs_to_jiffies(info->poll_int);
  74        schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  75}
  76
  77static void spu_gov_init_work(struct spu_gov_info_struct *info)
  78{
  79        int delay = usecs_to_jiffies(info->poll_int);
  80        INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
  81        schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  82}
  83
  84static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
  85{
  86        cancel_delayed_work_sync(&info->work);
  87}
  88
  89static int spu_gov_start(struct cpufreq_policy *policy)
  90{
  91        unsigned int cpu = policy->cpu;
  92        struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
  93        struct spu_gov_info_struct *affected_info;
  94        int i;
  95
  96        if (!cpu_online(cpu)) {
  97                printk(KERN_ERR "cpu %d is not online\n", cpu);
  98                return -EINVAL;
  99        }
 100
 101        if (!policy->cur) {
 102                printk(KERN_ERR "no cpu specified in policy\n");
 103                return -EINVAL;
 104        }
 105
 106        /* initialize spu_gov_info for all affected cpus */
 107        for_each_cpu(i, policy->cpus) {
 108                affected_info = &per_cpu(spu_gov_info, i);
 109                affected_info->policy = policy;
 110        }
 111
 112        info->poll_int = POLL_TIME;
 113
 114        /* setup timer */
 115        spu_gov_init_work(info);
 116
 117        return 0;
 118}
 119
 120static void spu_gov_stop(struct cpufreq_policy *policy)
 121{
 122        unsigned int cpu = policy->cpu;
 123        struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
 124        int i;
 125
 126        /* cancel timer */
 127        spu_gov_cancel_work(info);
 128
 129        /* clean spu_gov_info for all affected cpus */
 130        for_each_cpu (i, policy->cpus) {
 131                info = &per_cpu(spu_gov_info, i);
 132                info->policy = NULL;
 133        }
 134}
 135
 136static struct cpufreq_governor spu_governor = {
 137        .name = "spudemand",
 138        .start = spu_gov_start,
 139        .stop = spu_gov_stop,
 140        .owner = THIS_MODULE,
 141};
 142
 143/*
 144 * module init and destoy
 145 */
 146
 147static int __init spu_gov_init(void)
 148{
 149        int ret;
 150
 151        ret = cpufreq_register_governor(&spu_governor);
 152        if (ret)
 153                printk(KERN_ERR "registration of governor failed\n");
 154        return ret;
 155}
 156
 157static void __exit spu_gov_exit(void)
 158{
 159        cpufreq_unregister_governor(&spu_governor);
 160}
 161
 162
 163module_init(spu_gov_init);
 164module_exit(spu_gov_exit);
 165
 166MODULE_LICENSE("GPL");
 167MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 168
 169