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/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
  36 struct 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 };
  42 static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  43
  44 static 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
  59 static 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
  77 static 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
  84 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
  85 {
  86         cancel_delayed_work_sync(&info->work);
  87 }
  88
  89 static 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
 120 static 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
 136 static 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
 147 static 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
 157 static void __exit spu_gov_exit(void)
 158 {
 159         cpufreq_unregister_governor(&spu_governor);
 160 }
 161
 162
 163 module_init(spu_gov_init);
 164 module_exit(spu_gov_exit);
 165
 166 MODULE_LICENSE("GPL");
 167 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 168