drivers/cpufreq/cpufreq_conservative.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  drivers/cpufreq/cpufreq_conservative.c
   4  *
   5  *  Copyright (C)  2001 Russell King
   6  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   7  *                      Jun Nakajima <jun.nakajima@intel.com>
   8  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
   9  */
  10
  11 #include <linux/slab.h>
  12 #include "cpufreq_governor.h"
  13
  14 struct cs_policy_dbs_info {
  15         struct policy_dbs_info policy_dbs;
  16         unsigned int down_skip;
  17         unsigned int requested_freq;
  18 };
  19
  20 static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
  21 {
  22         return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
  23 }
  24
  25 struct cs_dbs_tuners {
  26         unsigned int down_threshold;
  27         unsigned int freq_step;
  28 };
  29
  30 /* Conservative governor macros */
  31 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  32 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
  33 #define DEF_FREQUENCY_STEP                      (5)
  34 #define DEF_SAMPLING_DOWN_FACTOR                (1)
  35 #define MAX_SAMPLING_DOWN_FACTOR                (10)
  36
  37 static inline unsigned int get_freq_step(struct cs_dbs_tuners *cs_tuners,
  38                                          struct cpufreq_policy *policy)
  39 {
  40         unsigned int freq_step = (cs_tuners->freq_step * policy->max) / 100;
  41
  42         /* max freq cannot be less than 100. But who knows... */
  43         if (unlikely(freq_step == 0))
  44                 freq_step = DEF_FREQUENCY_STEP;
  45
  46         return freq_step;
  47 }
  48
  49 /*
  50  * Every sampling_rate, we check, if current idle time is less than 20%
  51  * (default), then we try to increase frequency. Every sampling_rate *
  52  * sampling_down_factor, we check, if current idle time is more than 80%
  53  * (default), then we try to decrease frequency
  54  *
  55  * Frequency updates happen at minimum steps of 5% (default) of maximum
  56  * frequency
  57  */
  58 static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
  59 {
  60         struct policy_dbs_info *policy_dbs = policy->governor_data;
  61         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
  62         unsigned int requested_freq = dbs_info->requested_freq;
  63         struct dbs_data *dbs_data = policy_dbs->dbs_data;
  64         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
  65         unsigned int load = dbs_update(policy);
  66         unsigned int freq_step;
  67
  68         /*
  69          * break out if we 'cannot' reduce the speed as the user might
  70          * want freq_step to be zero
  71          */
  72         if (cs_tuners->freq_step == 0)
  73                 goto out;
  74
  75         /*
  76          * If requested_freq is out of range, it is likely that the limits
  77          * changed in the meantime, so fall back to current frequency in that
  78          * case.
  79          */
  80         if (requested_freq > policy->max || requested_freq < policy->min) {
  81                 requested_freq = policy->cur;
  82                 dbs_info->requested_freq = requested_freq;
  83         }
  84
  85         freq_step = get_freq_step(cs_tuners, policy);
  86
  87         /*
  88          * Decrease requested_freq one freq_step for each idle period that
  89          * we didn't update the frequency.
  90          */
  91         if (policy_dbs->idle_periods < UINT_MAX) {
  92                 unsigned int freq_steps = policy_dbs->idle_periods * freq_step;
  93
  94                 if (requested_freq > policy->min + freq_steps)
  95                         requested_freq -= freq_steps;
  96                 else
  97                         requested_freq = policy->min;
  98
  99                 policy_dbs->idle_periods = UINT_MAX;
 100         }
 101
 102         /* Check for frequency increase */
 103         if (load > dbs_data->up_threshold) {
 104                 dbs_info->down_skip = 0;
 105
 106                 /* if we are already at full speed then break out early */
 107                 if (requested_freq == policy->max)
 108                         goto out;
 109
 110                 requested_freq += freq_step;
 111                 if (requested_freq > policy->max)
 112                         requested_freq = policy->max;
 113
 114                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H);
 115                 dbs_info->requested_freq = requested_freq;
 116                 goto out;
 117         }
 118
 119         /* if sampling_down_factor is active break out early */
 120         if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
 121                 goto out;
 122         dbs_info->down_skip = 0;
 123
 124         /* Check for frequency decrease */
 125         if (load < cs_tuners->down_threshold) {
 126                 /*
 127                  * if we cannot reduce the frequency anymore, break out early
 128                  */
 129                 if (requested_freq == policy->min)
 130                         goto out;
 131
 132                 if (requested_freq > freq_step)
 133                         requested_freq -= freq_step;
 134                 else
 135                         requested_freq = policy->min;
 136
 137                 __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L);
 138                 dbs_info->requested_freq = requested_freq;
 139         }
 140
 141  out:
 142         return dbs_data->sampling_rate;
 143 }
 144
 145 /************************** sysfs interface ************************/
 146
 147 static ssize_t store_sampling_down_factor(struct gov_attr_set *attr_set,
 148                                           const char *buf, size_t count)
 149 {
 150         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 151         unsigned int input;
 152         int ret;
 153         ret = sscanf(buf, "%u", &input);
 154
 155         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 156                 return -EINVAL;
 157
 158         dbs_data->sampling_down_factor = input;
 159         return count;
 160 }
 161
 162 static ssize_t store_up_threshold(struct gov_attr_set *attr_set,
 163                                   const char *buf, size_t count)
 164 {
 165         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 166         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 167         unsigned int input;
 168         int ret;
 169         ret = sscanf(buf, "%u", &input);
 170
 171         if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
 172                 return -EINVAL;
 173
 174         dbs_data->up_threshold = input;
 175         return count;
 176 }
 177
 178 static ssize_t store_down_threshold(struct gov_attr_set *attr_set,
 179                                     const char *buf, size_t count)
 180 {
 181         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 182         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 183         unsigned int input;
 184         int ret;
 185         ret = sscanf(buf, "%u", &input);
 186
 187         /* cannot be lower than 1 otherwise freq will not fall */
 188         if (ret != 1 || input < 1 || input > 100 ||
 189                         input >= dbs_data->up_threshold)
 190                 return -EINVAL;
 191
 192         cs_tuners->down_threshold = input;
 193         return count;
 194 }
 195
 196 static ssize_t store_ignore_nice_load(struct gov_attr_set *attr_set,
 197                                       const char *buf, size_t count)
 198 {
 199         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 200         unsigned int input;
 201         int ret;
 202
 203         ret = sscanf(buf, "%u", &input);
 204         if (ret != 1)
 205                 return -EINVAL;
 206
 207         if (input > 1)
 208                 input = 1;
 209
 210         if (input == dbs_data->ignore_nice_load) /* nothing to do */
 211                 return count;
 212
 213         dbs_data->ignore_nice_load = input;
 214
 215         /* we need to re-evaluate prev_cpu_idle */
 216         gov_update_cpu_data(dbs_data);
 217
 218         return count;
 219 }
 220
 221 static ssize_t store_freq_step(struct gov_attr_set *attr_set, const char *buf,
 222                                size_t count)
 223 {
 224         struct dbs_data *dbs_data = to_dbs_data(attr_set);
 225         struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 226         unsigned int input;
 227         int ret;
 228         ret = sscanf(buf, "%u", &input);
 229
 230         if (ret != 1)
 231                 return -EINVAL;
 232
 233         if (input > 100)
 234                 input = 100;
 235
 236         /*
 237          * no need to test here if freq_step is zero as the user might actually
 238          * want this, they would be crazy though :)
 239          */
 240         cs_tuners->freq_step = input;
 241         return count;
 242 }
 243
 244 gov_show_one_common(sampling_rate);
 245 gov_show_one_common(sampling_down_factor);
 246 gov_show_one_common(up_threshold);
 247 gov_show_one_common(ignore_nice_load);
 248 gov_show_one(cs, down_threshold);
 249 gov_show_one(cs, freq_step);
 250
 251 gov_attr_rw(sampling_rate);
 252 gov_attr_rw(sampling_down_factor);
 253 gov_attr_rw(up_threshold);
 254 gov_attr_rw(ignore_nice_load);
 255 gov_attr_rw(down_threshold);
 256 gov_attr_rw(freq_step);
 257
 258 static struct attribute *cs_attributes[] = {
 259         &sampling_rate.attr,
 260         &sampling_down_factor.attr,
 261         &up_threshold.attr,
 262         &down_threshold.attr,
 263         &ignore_nice_load.attr,
 264         &freq_step.attr,
 265         NULL
 266 };
 267
 268 /************************** sysfs end ************************/
 269
 270 static struct policy_dbs_info *cs_alloc(void)
 271 {
 272         struct cs_policy_dbs_info *dbs_info;
 273
 274         dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
 275         return dbs_info ? &dbs_info->policy_dbs : NULL;
 276 }
 277
 278 static void cs_free(struct policy_dbs_info *policy_dbs)
 279 {
 280         kfree(to_dbs_info(policy_dbs));
 281 }
 282
 283 static int cs_init(struct dbs_data *dbs_data)
 284 {
 285         struct cs_dbs_tuners *tuners;
 286
 287         tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
 288         if (!tuners)
 289                 return -ENOMEM;
 290
 291         tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
 292         tuners->freq_step = DEF_FREQUENCY_STEP;
 293         dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
 294         dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
 295         dbs_data->ignore_nice_load = 0;
 296         dbs_data->tuners = tuners;
 297
 298         return 0;
 299 }
 300
 301 static void cs_exit(struct dbs_data *dbs_data)
 302 {
 303         kfree(dbs_data->tuners);
 304 }
 305
 306 static void cs_start(struct cpufreq_policy *policy)
 307 {
 308         struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
 309
 310         dbs_info->down_skip = 0;
 311         dbs_info->requested_freq = policy->cur;
 312 }
 313
 314 static struct dbs_governor cs_governor = {
 315         .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
 316         .kobj_type = { .default_attrs = cs_attributes },
 317         .gov_dbs_update = cs_dbs_update,
 318         .alloc = cs_alloc,
 319         .free = cs_free,
 320         .init = cs_init,
 321         .exit = cs_exit,
 322         .start = cs_start,
 323 };
 324
 325 #define CPU_FREQ_GOV_CONSERVATIVE       (cs_governor.gov)
 326
 327 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
 328 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
 329                 "Low Latency Frequency Transition capable processors "
 330                 "optimised for use in a battery environment");
 331 MODULE_LICENSE("GPL");
 332
 333 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
 334 struct cpufreq_governor *cpufreq_default_governor(void)
 335 {
 336         return &CPU_FREQ_GOV_CONSERVATIVE;
 337 }
 338 #endif
 339
 340 cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
 341 cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);