arch/powerpc/platforms/cell/cpufreq_spudemand.c

   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/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 µs */
  33 #define EXP             753             /* exp(-1) in fixed-point */
  34
  35 struct 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;          /* µs */
  40 };
  41 static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  42
  43 static 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
  58 static 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
  76 static 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
  83 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
  84 {
  85         cancel_delayed_work_sync(&info->work);
  86 }
  87
  88 static 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
 140 static 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
 150 static 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
 160 static void __exit spu_gov_exit(void)
 161 {
 162         cpufreq_unregister_governor(&spu_governor);
 163 }
 164
 165
 166 module_init(spu_gov_init);
 167 module_exit(spu_gov_exit);
 168
 169 MODULE_LICENSE("GPL");
 170 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 171