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
  86         freq_step = get_freq_step(cs_tuners, policy);
  87
  88         /*
  89          * Decrease requested_freq one freq_step for each idle period that
  90          * we didn't update the frequency.
  91          */
  92         if (policy_dbs->idle_periods < UINT_MAX) {
  93                 unsigned int freq_steps = policy_dbs->idle_periods * freq_step;
  94
  95                 if (requested_freq > freq_steps)
  96                         requested_freq -= freq_steps;
  97                 else
  98                         requested_freq = policy->min;
  99
 100                 policy_dbs->idle_periods = UINT_MAX;
 101         }
 102
 103         /* Check for frequency increase */
 104         if (load > dbs_data->up_threshold) {
 105                 dbs_info->down_skip = 0;
 106
 107                 /* if we are already at full speed then break out early */
 108                 if (requested_freq == policy->max)
 109                         goto out;
 110
 111                 requested_freq += freq_step;
 112                 if (requested_freq > policy->max)
 113                         requested_freq = policy->max;
 114
 115                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H);
 116                 dbs_info->requested_freq = requested_freq;
 117                 goto out;
 118         }
 119
 120         /* if sampling_down_factor is active break out early */
 121         if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
 122                 goto out;
 123         dbs_info->down_skip = 0;
 124
 125         /* Check for frequency decrease */
 126         if (load < cs_tuners->down_threshold) {
 127                 /*
 128                  * if we cannot reduce the frequency anymore, break out early
 129                  */
 130                 if (requested_freq == policy->min)
 131                         goto out;
 132
 133                 if (requested_freq > freq_step)
 134                         requested_freq -= freq_step;
 135                 else
 136                         requested_freq = policy->min;
 137
 138                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L);
 139                 dbs_info->requested_freq = requested_freq;
 140         }
 141
 142  out:
 143         return dbs_data->sampling_rate;
 144 }
 145
 146 /************************** sysfs interface ************************/
 147
 148 static ssize_t store_sampling_down_factor(struct gov_attr_set *attr_set,
 149                                           const char *buf, size_t count)
 150 {
 151         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 152         unsigned int input;
 153         int ret;
 154         ret = sscanf(buf, "%u", &input);
 155
 156         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 157                 return -EINVAL;
 158
 159         dbs_data->sampling_down_factor = input;
 160         return count;
 161 }
 162
 163 static ssize_t store_up_threshold(struct gov_attr_set *attr_set,
 164                                   const char *buf, size_t count)
 165 {
 166         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 167         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 168         unsigned int input;
 169         int ret;
 170         ret = sscanf(buf, "%u", &input);
 171
 172         if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
 173                 return -EINVAL;
 174
 175         dbs_data->up_threshold = input;
 176         return count;
 177 }
 178
 179 static ssize_t store_down_threshold(struct gov_attr_set *attr_set,
 180                                     const char *buf, size_t count)
 181 {
 182         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 183         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 184         unsigned int input;
 185         int ret;
 186         ret = sscanf(buf, "%u", &input);
 187
 188         /* cannot be lower than 1 otherwise freq will not fall */
 189         if (ret != 1 || input < 1 || input > 100 ||
 190                         input >= dbs_data->up_threshold)
 191                 return -EINVAL;
 192
 193         cs_tuners->down_threshold = input;
 194         return count;
 195 }
 196
 197 static ssize_t store_ignore_nice_load(struct gov_attr_set *attr_set,
 198                                       const char *buf, size_t count)
 199 {
 200         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 201         unsigned int input;
 202         int ret;
 203
 204         ret = sscanf(buf, "%u", &input);
 205         if (ret != 1)
 206                 return -EINVAL;
 207
 208         if (input > 1)
 209                 input = 1;
 210
 211         if (input == dbs_data->ignore_nice_load) /* nothing to do */
 212                 return count;
 213
 214         dbs_data->ignore_nice_load = input;
 215
 216         /* we need to re-evaluate prev_cpu_idle */
 217         gov_update_cpu_data(dbs_data);
 218
 219         return count;
 220 }
 221
 222 static ssize_t store_freq_step(struct gov_attr_set *attr_set, const char *buf,
 223                                size_t count)
 224 {
 225         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 226         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 227         unsigned int input;
 228         int ret;
 229         ret = sscanf(buf, "%u", &input);
 230
 231         if (ret != 1)
 232                 return -EINVAL;
 233
 234         if (input > 100)
 235                 input = 100;
 236
 237         /*
 238          * no need to test here if freq_step is zero as the user might actually
 239          * want this, they would be crazy though :)
 240          */
 241         cs_tuners->freq_step = input;
 242         return count;
 243 }
 244
 245 gov_show_one_common(sampling_rate);
 246 gov_show_one_common(sampling_down_factor);
 247 gov_show_one_common(up_threshold);
 248 gov_show_one_common(ignore_nice_load);
 249 gov_show_one_common(min_sampling_rate);
 250 gov_show_one(cs, down_threshold);
 251 gov_show_one(cs, freq_step);
 252
 253 gov_attr_rw(sampling_rate);
 254 gov_attr_rw(sampling_down_factor);
 255 gov_attr_rw(up_threshold);
 256 gov_attr_rw(ignore_nice_load);
 257 gov_attr_ro(min_sampling_rate);
 258 gov_attr_rw(down_threshold);
 259 gov_attr_rw(freq_step);
 260
 261 static struct attribute *cs_attributes[] = {
 262         &min_sampling_rate.attr,
 263         &sampling_rate.attr,
 264         &sampling_down_factor.attr,
 265         &up_threshold.attr,
 266         &down_threshold.attr,
 267         &ignore_nice_load.attr,
 268         &freq_step.attr,
 269         NULL
 270 };
 271
 272 /************************** sysfs end ************************/
 273
 274 static struct policy_dbs_info *cs_alloc(void)
 275 {
 276         struct cs_policy_dbs_info *dbs_info;
 277
 278         dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
 279         return dbs_info ? &dbs_info->policy_dbs : NULL;
 280 }
 281
 282 static void cs_free(struct policy_dbs_info *policy_dbs)
 283 {
 284         kfree(to_dbs_info(policy_dbs));
 285 }
 286
 287 static int cs_init(struct dbs_data *dbs_data)
 288 {
 289         struct cs_dbs_tuners *tuners;
 290
 291         tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
 292         if (!tuners)
 293                 return -ENOMEM;
 294
 295         tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
 296         tuners->freq_step = DEF_FREQUENCY_STEP;
 297         dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 298         dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 299         dbs_data->ignore_nice_load = 0;
 300
 301         dbs_data->tuners = tuners;
 302         dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
 303                 jiffies_to_usecs(10);
 304
 305         return 0;
 306 }
 307
 308 static void cs_exit(struct dbs_data *dbs_data)
 309 {
 310         kfree(dbs_data->tuners);
 311 }
 312
 313 static void cs_start(struct cpufreq_policy *policy)
 314 {
 315         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
 316
 317         dbs_info->down_skip = 0;
 318         dbs_info->requested_freq = policy->cur;
 319 }
 320
 321 static struct dbs_governor cs_governor = {
 322         .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
 323         .kobj_type = { .default_attrs = cs_attributes },
 324         .gov_dbs_update = cs_dbs_update,
 325         .alloc = cs_alloc,
 326         .free = cs_free,
 327         .init = cs_init,
 328         .exit = cs_exit,
 329         .start = cs_start,
 330 };
 331
 332 #define CPU_FREQ_GOV_CONSERVATIVE       (&cs_governor.gov)
 333
 334 static int __init cpufreq_gov_dbs_init(void)
 335 {
 336         return cpufreq_register_governor(CPU_FREQ_GOV_CONSERVATIVE);
 337 }
 338
 339 static void __exit cpufreq_gov_dbs_exit(void)
 340 {
 341         cpufreq_unregister_governor(CPU_FREQ_GOV_CONSERVATIVE);
 342 }
 343
 344 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 345 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 346                 "Low Latency Frequency Transition capable processors "
 347                 "optimised for use in a battery environment");
 348 MODULE_LICENSE("GPL");
 349
 350 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 351 struct cpufreq_governor *cpufreq_default_governor(void)
 352 {
 353         return CPU_FREQ_GOV_CONSERVATIVE;
 354 }
 355
 356 fs_initcall(cpufreq_gov_dbs_init);
 357 #else
 358 module_init(cpufreq_gov_dbs_init);
 359 #endif
 360 module_exit(cpufreq_gov_dbs_exit);