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/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
  34 struct 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 };
  40 static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
  41
  42 static int calc_freq(struct spu_gov_info_struct *info)
  43 {
  44         int cpu;
  45         int busy_spus;
  46
  47         cpu = info->policy->cpu;
  48         busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
  49
  50         CALC_LOAD(info->busy_spus, EXP, busy_spus * FIXED_1);
  51         pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
  52                         cpu, busy_spus, info->busy_spus);
  53
  54         return info->policy->max * info->busy_spus / FIXED_1;
  55 }
  56
  57 static void spu_gov_work(struct work_struct *work)
  58 {
  59         struct spu_gov_info_struct *info;
  60         int delay;
  61         unsigned long target_freq;
  62
  63         info = container_of(work, struct spu_gov_info_struct, work.work);
  64
  65         /* after cancel_delayed_work_sync we unset info->policy */
  66         BUG_ON(info->policy == NULL);
  67
  68         target_freq = calc_freq(info);
  69         __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
  70
  71         delay = usecs_to_jiffies(info->poll_int);
  72         schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  73 }
  74
  75 static void spu_gov_init_work(struct spu_gov_info_struct *info)
  76 {
  77         int delay = usecs_to_jiffies(info->poll_int);
  78         INIT_DELAYED_WORK_DEFERRABLE(&info->work, spu_gov_work);
  79         schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
  80 }
  81
  82 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
  83 {
  84         cancel_delayed_work_sync(&info->work);
  85 }
  86
  87 static int spu_gov_govern(struct cpufreq_policy *policy, unsigned int event)
  88 {
  89         unsigned int cpu = policy->cpu;
  90         struct spu_gov_info_struct *info, *affected_info;
  91         int i;
  92         int ret = 0;
  93
  94         info = &per_cpu(spu_gov_info, cpu);
  95
  96         switch (event) {
  97         case CPUFREQ_GOV_START:
  98                 if (!cpu_online(cpu)) {
  99                         printk(KERN_ERR "cpu %d is not online\n", cpu);
 100                         ret = -EINVAL;
 101                         break;
 102                 }
 103
 104                 if (!policy->cur) {
 105                         printk(KERN_ERR "no cpu specified in policy\n");
 106                         ret = -EINVAL;
 107                         break;
 108                 }
 109
 110                 /* initialize spu_gov_info for all affected cpus */
 111                 for_each_cpu(i, policy->cpus) {
 112                         affected_info = &per_cpu(spu_gov_info, i);
 113                         affected_info->policy = policy;
 114                 }
 115
 116                 info->poll_int = POLL_TIME;
 117
 118                 /* setup timer */
 119                 spu_gov_init_work(info);
 120
 121                 break;
 122
 123         case CPUFREQ_GOV_STOP:
 124                 /* cancel timer */
 125                 spu_gov_cancel_work(info);
 126
 127                 /* clean spu_gov_info for all affected cpus */
 128                 for_each_cpu (i, policy->cpus) {
 129                         info = &per_cpu(spu_gov_info, i);
 130                         info->policy = NULL;
 131                 }
 132
 133                 break;
 134         }
 135
 136         return ret;
 137 }
 138
 139 static struct cpufreq_governor spu_governor = {
 140         .name = "spudemand",
 141         .governor = spu_gov_govern,
 142         .owner = THIS_MODULE,
 143 };
 144
 145 /*
 146  * module init and destoy
 147  */
 148
 149 static int __init spu_gov_init(void)
 150 {
 151         int ret;
 152
 153         ret = cpufreq_register_governor(&spu_governor);
 154         if (ret)
 155                 printk(KERN_ERR "registration of governor failed\n");
 156         return ret;
 157 }
 158
 159 static void __exit spu_gov_exit(void)
 160 {
 161         cpufreq_unregister_governor(&spu_governor);
 162 }
 163
 164
 165 module_init(spu_gov_init);
 166 module_exit(spu_gov_exit);
 167
 168 MODULE_LICENSE("GPL");
 169 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 170