platforms/cell/cpufreq_spudemand.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * spu aware cpufreq governor for the cell processor
0004  *
0005  * © Copyright IBM Corporation 2006-2008
0006  *
0007  * Author: Christian Krafft <krafft@de.ibm.com>
0008  */
0009
0010 #include <linux/cpufreq.h>
0011 #include <linux/sched.h>
0012 #include <linux/sched/loadavg.h>
0013 #include <linux/module.h>
0014 #include <linux/timer.h>
0015 #include <linux/workqueue.h>
0016 #include <linux/atomic.h>
0017 #include <asm/machdep.h>
0018 #include <asm/spu.h>
0019
0020 #define POLL_TIME   100000      /* in µs */
0021 #define EXP     753     /* exp(-1) in fixed-point */
0022
0023 struct spu_gov_info_struct {
0024     unsigned long busy_spus;    /* fixed-point */
0025     struct cpufreq_policy *policy;
0026     struct delayed_work work;
0027     unsigned int poll_int;      /* µs */
0028 };
0029 static DEFINE_PER_CPU(struct spu_gov_info_struct, spu_gov_info);
0030
0031 static int calc_freq(struct spu_gov_info_struct *info)
0032 {
0033     int cpu;
0034     int busy_spus;
0035
0036     cpu = info->policy->cpu;
0037     busy_spus = atomic_read(&cbe_spu_info[cpu_to_node(cpu)].busy_spus);
0038
0039     info->busy_spus = calc_load(info->busy_spus, EXP, busy_spus * FIXED_1);
0040     pr_debug("cpu %d: busy_spus=%d, info->busy_spus=%ld\n",
0041             cpu, busy_spus, info->busy_spus);
0042
0043     return info->policy->max * info->busy_spus / FIXED_1;
0044 }
0045
0046 static void spu_gov_work(struct work_struct *work)
0047 {
0048     struct spu_gov_info_struct *info;
0049     int delay;
0050     unsigned long target_freq;
0051
0052     info = container_of(work, struct spu_gov_info_struct, work.work);
0053
0054     /* after cancel_delayed_work_sync we unset info->policy */
0055     BUG_ON(info->policy == NULL);
0056
0057     target_freq = calc_freq(info);
0058     __cpufreq_driver_target(info->policy, target_freq, CPUFREQ_RELATION_H);
0059
0060     delay = usecs_to_jiffies(info->poll_int);
0061     schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
0062 }
0063
0064 static void spu_gov_init_work(struct spu_gov_info_struct *info)
0065 {
0066     int delay = usecs_to_jiffies(info->poll_int);
0067     INIT_DEFERRABLE_WORK(&info->work, spu_gov_work);
0068     schedule_delayed_work_on(info->policy->cpu, &info->work, delay);
0069 }
0070
0071 static void spu_gov_cancel_work(struct spu_gov_info_struct *info)
0072 {
0073     cancel_delayed_work_sync(&info->work);
0074 }
0075
0076 static int spu_gov_start(struct cpufreq_policy *policy)
0077 {
0078     unsigned int cpu = policy->cpu;
0079     struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
0080     struct spu_gov_info_struct *affected_info;
0081     int i;
0082
0083     if (!cpu_online(cpu)) {
0084         printk(KERN_ERR "cpu %d is not online\n", cpu);
0085         return -EINVAL;
0086     }
0087
0088     if (!policy->cur) {
0089         printk(KERN_ERR "no cpu specified in policy\n");
0090         return -EINVAL;
0091     }
0092
0093     /* initialize spu_gov_info for all affected cpus */
0094     for_each_cpu(i, policy->cpus) {
0095         affected_info = &per_cpu(spu_gov_info, i);
0096         affected_info->policy = policy;
0097     }
0098
0099     info->poll_int = POLL_TIME;
0100
0101     /* setup timer */
0102     spu_gov_init_work(info);
0103
0104     return 0;
0105 }
0106
0107 static void spu_gov_stop(struct cpufreq_policy *policy)
0108 {
0109     unsigned int cpu = policy->cpu;
0110     struct spu_gov_info_struct *info = &per_cpu(spu_gov_info, cpu);
0111     int i;
0112
0113     /* cancel timer */
0114     spu_gov_cancel_work(info);
0115
0116     /* clean spu_gov_info for all affected cpus */
0117     for_each_cpu (i, policy->cpus) {
0118         info = &per_cpu(spu_gov_info, i);
0119         info->policy = NULL;
0120     }
0121 }
0122
0123 static struct cpufreq_governor spu_governor = {
0124     .name = "spudemand",
0125     .start = spu_gov_start,
0126     .stop = spu_gov_stop,
0127     .owner = THIS_MODULE,
0128 };
0129 cpufreq_governor_init(spu_governor);
0130 cpufreq_governor_exit(spu_governor);
0131
0132 MODULE_LICENSE("GPL");
0133 MODULE_AUTHOR("Christian Krafft <krafft@de.ibm.com>");