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/timer.h>
  26#include <linux/workqueue.h>
  27#include <asm/atomic.h>
  28#include <asm/machdep.h>
  29#include <asm/spu.h>
  30
  31#define POLL_TIME       100000          /* in µs */
  32#define EXP             753             /* exp(-1) in fixed-point */
  33
  34struct spu_gov_info_struct {
  35        unsigned long busy_spus;        /* fixed-point */
  36        struct cpufreq_policy *policy;
  37        struct delayed_work work;
  38        unsigned int poll_int;          /* µs */
  39};
  40static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  41
  42static struct workqueue_struct *kspugov_wq;
  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        queue_delayed_work_on(info->policy->cpu, kspugov_wq, &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_DELAYED_WORK_DEFERRABLE(&info->work, spu_gov_work);
  81        queue_delayed_work_on(info->policy->cpu, kspugov_wq, &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_govern(struct cpufreq_policy *policy, unsigned int event)
  90{
  91        unsigned int cpu = policy->cpu;
  92        struct spu_gov_info_struct *info, *affected_info;
  93        int i;
  94        int ret = 0;
  95
  96        info = &per_cpu(spu_gov_info, cpu);
  97
  98        switch (event) {
  99        case CPUFREQ_GOV_START:
 100                if (!cpu_online(cpu)) {
 101                        printk(KERN_ERR "cpu %d is not online\n", cpu);
 102                        ret = -EINVAL;
 103                        break;
 104                }
 105
 106                if (!policy->cur) {
 107                        printk(KERN_ERR "no cpu specified in policy\n");
 108                        ret = -EINVAL;
 109                        break;
 110                }
 111
 112                /* initialize spu_gov_info for all affected cpus */
 113                for_each_cpu(i, policy->cpus) {
 114                        affected_info = &per_cpu(spu_gov_info, i);
 115                        affected_info->policy = policy;
 116                }
 117
 118                info->poll_int = POLL_TIME;
 119
 120                /* setup timer */
 121                spu_gov_init_work(info);
 122
 123                break;
 124
 125        case CPUFREQ_GOV_STOP:
 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                break;
 136        }
 137
 138        return ret;
 139}
 140
 141static struct cpufreq_governor spu_governor = {
 142        .name = "spudemand",
 143        .governor = spu_gov_govern,
 144        .owner = THIS_MODULE,
 145};
 146
 147/*
 148 * module init and destoy
 149 */
 150
 151static int __init spu_gov_init(void)
 152{
 153        int ret;
 154
 155        kspugov_wq = create_workqueue("kspugov");
 156        if (!kspugov_wq) {
 157                printk(KERN_ERR "creation of kspugov failed\n");
 158                ret = -EFAULT;
 159                goto out;
 160        }
 161
 162        ret = cpufreq_register_governor(&spu_governor);
 163        if (ret) {
 164                printk(KERN_ERR "registration of governor failed\n");
 165                destroy_workqueue(kspugov_wq);
 166                goto out;
 167        }
 168out:
 169        return ret;
 170}
 171
 172static void __exit spu_gov_exit(void)
 173{
 174        cpufreq_unregister_governor(&spu_governor);
 175        destroy_workqueue(kspugov_wq);
 176}
 177
 178
 179module_init(spu_gov_init);
 180module_exit(spu_gov_exit);
 181
 182MODULE_LICENSE("GPL");
 183MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 184
 185