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 
171