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Linux/arch/powerpc/platforms/cell/cpufreq_spudemand.c

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  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_DEFERRABLE_WORK(&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 
172 

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