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
calc_freq(struct spu_gov_info_struct * info)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
spu_gov_work(struct work_struct * work)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
spu_gov_init_work(struct spu_gov_info_struct * info)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
spu_gov_cancel_work(struct spu_gov_info_struct * info)83 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
84 {
85 cancel_delayed_work_sync(&info->work);
86 }
87
spu_gov_govern(struct cpufreq_policy * policy,unsigned int event)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
spu_gov_init(void)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
spu_gov_exit(void)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