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_DELAYED_WORK_DEFERRABLE(&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