drivers/cpufreq/cpufreq_conservative.c

   1 /*
   2  *  drivers/cpufreq/cpufreq_conservative.c
   3  *
   4  *  Copyright (C)  2001 Russell King
   5  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   6  *                      Jun Nakajima <jun.nakajima@intel.com>
   7  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/slab.h>
  15 #include "cpufreq_governor.h"
  16
  17 struct cs_policy_dbs_info {
  18         struct policy_dbs_info policy_dbs;
  19         unsigned int down_skip;
  20         unsigned int requested_freq;
  21 };
  22
  23 static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
  24 {
  25         return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
  26 }
  27
  28 struct cs_dbs_tuners {
  29         unsigned int down_threshold;
  30         unsigned int freq_step;
  31 };
  32
  33 /* Conservative governor macros */
  34 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  35 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  36 #define DEF_FREQUENCY_STEP                      (5)
  37 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  38 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  39
  40 static inline unsigned int get_freq_step(struct cs_dbs_tuners *cs_tuners,
  41                                          struct cpufreq_policy *policy)
  42 {
  43         unsigned int freq_step = (cs_tuners->freq_step * policy->max) / 100;
  44
  45         /* max freq cannot be less than 100. But who knows... */
  46         if (unlikely(freq_step == 0))
  47                 freq_step = DEF_FREQUENCY_STEP;
  48
  49         return freq_step;
  50 }
  51
  52 /*
  53  * Every sampling_rate, we check, if current idle time is less than 20%
  54  * (default), then we try to increase frequency. Every sampling_rate *
  55  * sampling_down_factor, we check, if current idle time is more than 80%
  56  * (default), then we try to decrease frequency
  57  *
  58  * Frequency updates happen at minimum steps of 5% (default) of maximum
  59  * frequency
  60  */
  61 static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
  62 {
  63         struct policy_dbs_info *policy_dbs = policy->governor_data;
  64         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
  65         unsigned int requested_freq = dbs_info->requested_freq;
  66         struct dbs_data *dbs_data = policy_dbs->dbs_data;
  67         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  68         unsigned int load = dbs_update(policy);
  69         unsigned int freq_step;
  70
  71         /*
  72          * break out if we 'cannot' reduce the speed as the user might
  73          * want freq_step to be zero
  74          */
  75         if (cs_tuners->freq_step == 0)
  76                 goto out;
  77
  78         /*
  79          * If requested_freq is out of range, it is likely that the limits
  80          * changed in the meantime, so fall back to current frequency in that
  81          * case.
  82          */
  83         if (requested_freq > policy->max || requested_freq < policy->min) {
  84                 requested_freq = policy->cur;
  85                 dbs_info->requested_freq = requested_freq;
  86         }
  87
  88         freq_step = get_freq_step(cs_tuners, policy);
  89
  90         /*
  91          * Decrease requested_freq one freq_step for each idle period that
  92          * we didn't update the frequency.
  93          */
  94         if (policy_dbs->idle_periods < UINT_MAX) {
  95                 unsigned int freq_steps = policy_dbs->idle_periods * freq_step;
  96
  97                 if (requested_freq > policy->min + freq_steps)
  98                         requested_freq -= freq_steps;
  99                 else
 100                         requested_freq = policy->min;
 101
 102                 policy_dbs->idle_periods = UINT_MAX;
 103         }
 104
 105         /* Check for frequency increase */
 106         if (load > dbs_data->up_threshold) {
 107                 dbs_info->down_skip = 0;
 108
 109                 /* if we are already at full speed then break out early */
 110                 if (requested_freq == policy->max)
 111                         goto out;
 112
 113                 requested_freq += freq_step;
 114                 if (requested_freq > policy->max)
 115                         requested_freq = policy->max;
 116
 117                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H);
 118                 dbs_info->requested_freq = requested_freq;
 119                 goto out;
 120         }
 121
 122         /* if sampling_down_factor is active break out early */
 123         if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
 124                 goto out;
 125         dbs_info->down_skip = 0;
 126
 127         /* Check for frequency decrease */
 128         if (load < cs_tuners->down_threshold) {
 129                 /*
 130                  * if we cannot reduce the frequency anymore, break out early
 131                  */
 132                 if (requested_freq == policy->min)
 133                         goto out;
 134
 135                 if (requested_freq > freq_step)
 136                         requested_freq -= freq_step;
 137                 else
 138                         requested_freq = policy->min;
 139
 140                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L);
 141                 dbs_info->requested_freq = requested_freq;
 142         }
 143
 144  out:
 145         return dbs_data->sampling_rate;
 146 }
 147
 148 /************************** sysfs interface ************************/
 149
 150 static ssize_t store_sampling_down_factor(struct gov_attr_set *attr_set,
 151                                           const char *buf, size_t count)
 152 {
 153         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 154         unsigned int input;
 155         int ret;
 156         ret = sscanf(buf, "%u", &input);
 157
 158         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 159                 return -EINVAL;
 160
 161         dbs_data->sampling_down_factor = input;
 162         return count;
 163 }
 164
 165 static ssize_t store_up_threshold(struct gov_attr_set *attr_set,
 166                                   const char *buf, size_t count)
 167 {
 168         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 169         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 170         unsigned int input;
 171         int ret;
 172         ret = sscanf(buf, "%u", &input);
 173
 174         if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
 175                 return -EINVAL;
 176
 177         dbs_data->up_threshold = input;
 178         return count;
 179 }
 180
 181 static ssize_t store_down_threshold(struct gov_attr_set *attr_set,
 182                                     const char *buf, size_t count)
 183 {
 184         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 185         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 186         unsigned int input;
 187         int ret;
 188         ret = sscanf(buf, "%u", &input);
 189
 190         /* cannot be lower than 1 otherwise freq will not fall */
 191         if (ret != 1 || input < 1 || input > 100 ||
 192                         input >= dbs_data->up_threshold)
 193                 return -EINVAL;
 194
 195         cs_tuners->down_threshold = input;
 196         return count;
 197 }
 198
 199 static ssize_t store_ignore_nice_load(struct gov_attr_set *attr_set,
 200                                       const char *buf, size_t count)
 201 {
 202         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 203         unsigned int input;
 204         int ret;
 205
 206         ret = sscanf(buf, "%u", &input);
 207         if (ret != 1)
 208                 return -EINVAL;
 209
 210         if (input > 1)
 211                 input = 1;
 212
 213         if (input == dbs_data->ignore_nice_load) /* nothing to do */
 214                 return count;
 215
 216         dbs_data->ignore_nice_load = input;
 217
 218         /* we need to re-evaluate prev_cpu_idle */
 219         gov_update_cpu_data(dbs_data);
 220
 221         return count;
 222 }
 223
 224 static ssize_t store_freq_step(struct gov_attr_set *attr_set, const char *buf,
 225                                size_t count)
 226 {
 227         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 228         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 229         unsigned int input;
 230         int ret;
 231         ret = sscanf(buf, "%u", &input);
 232
 233         if (ret != 1)
 234                 return -EINVAL;
 235
 236         if (input > 100)
 237                 input = 100;
 238
 239         /*
 240          * no need to test here if freq_step is zero as the user might actually
 241          * want this, they would be crazy though :)
 242          */
 243         cs_tuners->freq_step = input;
 244         return count;
 245 }
 246
 247 gov_show_one_common(sampling_rate);
 248 gov_show_one_common(sampling_down_factor);
 249 gov_show_one_common(up_threshold);
 250 gov_show_one_common(ignore_nice_load);
 251 gov_show_one(cs, down_threshold);
 252 gov_show_one(cs, freq_step);
 253
 254 gov_attr_rw(sampling_rate);
 255 gov_attr_rw(sampling_down_factor);
 256 gov_attr_rw(up_threshold);
 257 gov_attr_rw(ignore_nice_load);
 258 gov_attr_rw(down_threshold);
 259 gov_attr_rw(freq_step);
 260
 261 static struct attribute *cs_attributes[] = {
 262         &sampling_rate.attr,
 263         &sampling_down_factor.attr,
 264         &up_threshold.attr,
 265         &down_threshold.attr,
 266         &ignore_nice_load.attr,
 267         &freq_step.attr,
 268         NULL
 269 };
 270
 271 /************************** sysfs end ************************/
 272
 273 static struct policy_dbs_info *cs_alloc(void)
 274 {
 275         struct cs_policy_dbs_info *dbs_info;
 276
 277         dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
 278         return dbs_info ? &dbs_info->policy_dbs : NULL;
 279 }
 280
 281 static void cs_free(struct policy_dbs_info *policy_dbs)
 282 {
 283         kfree(to_dbs_info(policy_dbs));
 284 }
 285
 286 static int cs_init(struct dbs_data *dbs_data)
 287 {
 288         struct cs_dbs_tuners *tuners;
 289
 290         tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
 291         if (!tuners)
 292                 return -ENOMEM;
 293
 294         tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
 295         tuners->freq_step = DEF_FREQUENCY_STEP;
 296         dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 297         dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 298         dbs_data->ignore_nice_load = 0;
 299         dbs_data->tuners = tuners;
 300
 301         return 0;
 302 }
 303
 304 static void cs_exit(struct dbs_data *dbs_data)
 305 {
 306         kfree(dbs_data->tuners);
 307 }
 308
 309 static void cs_start(struct cpufreq_policy *policy)
 310 {
 311         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
 312
 313         dbs_info->down_skip = 0;
 314         dbs_info->requested_freq = policy->cur;
 315 }
 316
 317 static struct dbs_governor cs_governor = {
 318         .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
 319         .kobj_type = { .default_attrs = cs_attributes },
 320         .gov_dbs_update = cs_dbs_update,
 321         .alloc = cs_alloc,
 322         .free = cs_free,
 323         .init = cs_init,
 324         .exit = cs_exit,
 325         .start = cs_start,
 326 };
 327
 328 #define CPU_FREQ_GOV_CONSERVATIVE       (&cs_governor.gov)
 329
 330 static int __init cpufreq_gov_dbs_init(void)
 331 {
 332         return cpufreq_register_governor(CPU_FREQ_GOV_CONSERVATIVE);
 333 }
 334
 335 static void __exit cpufreq_gov_dbs_exit(void)
 336 {
 337         cpufreq_unregister_governor(CPU_FREQ_GOV_CONSERVATIVE);
 338 }
 339
 340 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 341 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 342                 "Low Latency Frequency Transition capable processors "
 343                 "optimised for use in a battery environment");
 344 MODULE_LICENSE("GPL");
 345
 346 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 347 struct cpufreq_governor *cpufreq_default_governor(void)
 348 {
 349         return CPU_FREQ_GOV_CONSERVATIVE;
 350 }
 351
 352 fs_initcall(cpufreq_gov_dbs_init);
 353 #else
 354 module_init(cpufreq_gov_dbs_init);
 355 #endif
 356 module_exit(cpufreq_gov_dbs_exit);