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 struct workqueue_struct *kspugov_wq;
  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         queue_delayed_work_on(info->policy->cpu, kspugov_wq, &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_DELAYED_WORK_DEFERRABLE(&info->work, spu_gov_work);
  81         queue_delayed_work_on(info->policy->cpu, kspugov_wq, &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_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_mask(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_mask (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
 141 static 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
 151 static 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         }
 168 out:
 169         return ret;
 170 }
 171
 172 static void __exit spu_gov_exit(void)
 173 {
 174         cpufreq_unregister_governor(&spu_governor);
 175         destroy_workqueue(kspugov_wq);
 176 }
 177
 178
 179 module_init(spu_gov_init);
 180 module_exit(spu_gov_exit);
 181
 182 MODULE_LICENSE("GPL");
 183 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");
 184