drivers/cpufreq/cpufreq_conservative.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  drivers/cpufreq/cpufreq_conservative.c
0004  *
0005  *  Copyright (C)  2001 Russell King
0006  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
0007  *                      Jun Nakajima <jun.nakajima@intel.com>
0008  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
0009  */
0010
0011 #include <linux/slab.h>
0012 #include "cpufreq_governor.h"
0013
0014 struct cs_policy_dbs_info {
0015     struct policy_dbs_info policy_dbs;
0016     unsigned int down_skip;
0017     unsigned int requested_freq;
0018 };
0019
0020 static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
0021 {
0022     return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
0023 }
0024
0025 struct cs_dbs_tuners {
0026     unsigned int down_threshold;
0027     unsigned int freq_step;
0028 };
0029
0030 /* Conservative governor macros */
0031 #define DEF_FREQUENCY_UP_THRESHOLD      (80)
0032 #define DEF_FREQUENCY_DOWN_THRESHOLD        (20)
0033 #define DEF_FREQUENCY_STEP          (5)
0034 #define DEF_SAMPLING_DOWN_FACTOR        (1)
0035 #define MAX_SAMPLING_DOWN_FACTOR        (10)
0036
0037 static inline unsigned int get_freq_step(struct cs_dbs_tuners *cs_tuners,
0038                      struct cpufreq_policy *policy)
0039 {
0040     unsigned int freq_step = (cs_tuners->freq_step * policy->max) / 100;
0041
0042     /* max freq cannot be less than 100. But who knows... */
0043     if (unlikely(freq_step == 0))
0044         freq_step = DEF_FREQUENCY_STEP;
0045
0046     return freq_step;
0047 }
0048
0049 /*
0050  * Every sampling_rate, we check, if current idle time is less than 20%
0051  * (default), then we try to increase frequency. Every sampling_rate *
0052  * sampling_down_factor, we check, if current idle time is more than 80%
0053  * (default), then we try to decrease frequency
0054  *
0055  * Frequency updates happen at minimum steps of 5% (default) of maximum
0056  * frequency
0057  */
0058 static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
0059 {
0060     struct policy_dbs_info *policy_dbs = policy->governor_data;
0061     struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
0062     unsigned int requested_freq = dbs_info->requested_freq;
0063     struct dbs_data *dbs_data = policy_dbs->dbs_data;
0064     struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
0065     unsigned int load = dbs_update(policy);
0066     unsigned int freq_step;
0067
0068     /*
0069      * break out if we 'cannot' reduce the speed as the user might
0070      * want freq_step to be zero
0071      */
0072     if (cs_tuners->freq_step == 0)
0073         goto out;
0074
0075     /*
0076      * If requested_freq is out of range, it is likely that the limits
0077      * changed in the meantime, so fall back to current frequency in that
0078      * case.
0079      */
0080     if (requested_freq > policy->max || requested_freq < policy->min) {
0081         requested_freq = policy->cur;
0082         dbs_info->requested_freq = requested_freq;
0083     }
0084
0085     freq_step = get_freq_step(cs_tuners, policy);
0086
0087     /*
0088      * Decrease requested_freq one freq_step for each idle period that
0089      * we didn't update the frequency.
0090      */
0091     if (policy_dbs->idle_periods < UINT_MAX) {
0092         unsigned int freq_steps = policy_dbs->idle_periods * freq_step;
0093
0094         if (requested_freq > policy->min + freq_steps)
0095             requested_freq -= freq_steps;
0096         else
0097             requested_freq = policy->min;
0098
0099         policy_dbs->idle_periods = UINT_MAX;
0100     }
0101
0102     /* Check for frequency increase */
0103     if (load > dbs_data->up_threshold) {
0104         dbs_info->down_skip = 0;
0105
0106         /* if we are already at full speed then break out early */
0107         if (requested_freq == policy->max)
0108             goto out;
0109
0110         requested_freq += freq_step;
0111         if (requested_freq > policy->max)
0112             requested_freq = policy->max;
0113
0114         __cpufreq_driver_target(policy, requested_freq,
0115                     CPUFREQ_RELATION_HE);
0116         dbs_info->requested_freq = requested_freq;
0117         goto out;
0118     }
0119
0120     /* if sampling_down_factor is active break out early */
0121     if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
0122         goto out;
0123     dbs_info->down_skip = 0;
0124
0125     /* Check for frequency decrease */
0126     if (load < cs_tuners->down_threshold) {
0127         /*
0128          * if we cannot reduce the frequency anymore, break out early
0129          */
0130         if (requested_freq == policy->min)
0131             goto out;
0132
0133         if (requested_freq > freq_step)
0134             requested_freq -= freq_step;
0135         else
0136             requested_freq = policy->min;
0137
0138         __cpufreq_driver_target(policy, requested_freq,
0139                     CPUFREQ_RELATION_LE);
0140         dbs_info->requested_freq = requested_freq;
0141     }
0142
0143  out:
0144     return dbs_data->sampling_rate;
0145 }
0146
0147 /************************** sysfs interface ************************/
0148
0149 static ssize_t sampling_down_factor_store(struct gov_attr_set *attr_set,
0150                       const char *buf, size_t count)
0151 {
0152     struct dbs_data *dbs_data = to_dbs_data(attr_set);
0153     unsigned int input;
0154     int ret;
0155     ret = sscanf(buf, "%u", &input);
0156
0157     if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
0158         return -EINVAL;
0159
0160     dbs_data->sampling_down_factor = input;
0161     return count;
0162 }
0163
0164 static ssize_t up_threshold_store(struct gov_attr_set *attr_set,
0165                   const char *buf, size_t count)
0166 {
0167     struct dbs_data *dbs_data = to_dbs_data(attr_set);
0168     struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
0169     unsigned int input;
0170     int ret;
0171     ret = sscanf(buf, "%u", &input);
0172
0173     if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
0174         return -EINVAL;
0175
0176     dbs_data->up_threshold = input;
0177     return count;
0178 }
0179
0180 static ssize_t down_threshold_store(struct gov_attr_set *attr_set,
0181                     const char *buf, size_t count)
0182 {
0183     struct dbs_data *dbs_data = to_dbs_data(attr_set);
0184     struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
0185     unsigned int input;
0186     int ret;
0187     ret = sscanf(buf, "%u", &input);
0188
0189     /* cannot be lower than 1 otherwise freq will not fall */
0190     if (ret != 1 || input < 1 || input > 100 ||
0191             input >= dbs_data->up_threshold)
0192         return -EINVAL;
0193
0194     cs_tuners->down_threshold = input;
0195     return count;
0196 }
0197
0198 static ssize_t ignore_nice_load_store(struct gov_attr_set *attr_set,
0199                       const char *buf, size_t count)
0200 {
0201     struct dbs_data *dbs_data = to_dbs_data(attr_set);
0202     unsigned int input;
0203     int ret;
0204
0205     ret = sscanf(buf, "%u", &input);
0206     if (ret != 1)
0207         return -EINVAL;
0208
0209     if (input > 1)
0210         input = 1;
0211
0212     if (input == dbs_data->ignore_nice_load) /* nothing to do */
0213         return count;
0214
0215     dbs_data->ignore_nice_load = input;
0216
0217     /* we need to re-evaluate prev_cpu_idle */
0218     gov_update_cpu_data(dbs_data);
0219
0220     return count;
0221 }
0222
0223 static ssize_t freq_step_store(struct gov_attr_set *attr_set, const char *buf,
0224                    size_t count)
0225 {
0226     struct dbs_data *dbs_data = to_dbs_data(attr_set);
0227     struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
0228     unsigned int input;
0229     int ret;
0230     ret = sscanf(buf, "%u", &input);
0231
0232     if (ret != 1)
0233         return -EINVAL;
0234
0235     if (input > 100)
0236         input = 100;
0237
0238     /*
0239      * no need to test here if freq_step is zero as the user might actually
0240      * want this, they would be crazy though :)
0241      */
0242     cs_tuners->freq_step = input;
0243     return count;
0244 }
0245
0246 gov_show_one_common(sampling_rate);
0247 gov_show_one_common(sampling_down_factor);
0248 gov_show_one_common(up_threshold);
0249 gov_show_one_common(ignore_nice_load);
0250 gov_show_one(cs, down_threshold);
0251 gov_show_one(cs, freq_step);
0252
0253 gov_attr_rw(sampling_rate);
0254 gov_attr_rw(sampling_down_factor);
0255 gov_attr_rw(up_threshold);
0256 gov_attr_rw(ignore_nice_load);
0257 gov_attr_rw(down_threshold);
0258 gov_attr_rw(freq_step);
0259
0260 static struct attribute *cs_attrs[] = {
0261     &sampling_rate.attr,
0262     &sampling_down_factor.attr,
0263     &up_threshold.attr,
0264     &down_threshold.attr,
0265     &ignore_nice_load.attr,
0266     &freq_step.attr,
0267     NULL
0268 };
0269 ATTRIBUTE_GROUPS(cs);
0270
0271 /************************** sysfs end ************************/
0272
0273 static struct policy_dbs_info *cs_alloc(void)
0274 {
0275     struct cs_policy_dbs_info *dbs_info;
0276
0277     dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
0278     return dbs_info ? &dbs_info->policy_dbs : NULL;
0279 }
0280
0281 static void cs_free(struct policy_dbs_info *policy_dbs)
0282 {
0283     kfree(to_dbs_info(policy_dbs));
0284 }
0285
0286 static int cs_init(struct dbs_data *dbs_data)
0287 {
0288     struct cs_dbs_tuners *tuners;
0289
0290     tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
0291     if (!tuners)
0292         return -ENOMEM;
0293
0294     tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
0295     tuners->freq_step = DEF_FREQUENCY_STEP;
0296     dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
0297     dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
0298     dbs_data->ignore_nice_load = 0;
0299     dbs_data->tuners = tuners;
0300
0301     return 0;
0302 }
0303
0304 static void cs_exit(struct dbs_data *dbs_data)
0305 {
0306     kfree(dbs_data->tuners);
0307 }
0308
0309 static void cs_start(struct cpufreq_policy *policy)
0310 {
0311     struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
0312
0313     dbs_info->down_skip = 0;
0314     dbs_info->requested_freq = policy->cur;
0315 }
0316
0317 static struct dbs_governor cs_governor = {
0318     .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
0319     .kobj_type = { .default_groups = cs_groups },
0320     .gov_dbs_update = cs_dbs_update,
0321     .alloc = cs_alloc,
0322     .free = cs_free,
0323     .init = cs_init,
0324     .exit = cs_exit,
0325     .start = cs_start,
0326 };
0327
0328 #define CPU_FREQ_GOV_CONSERVATIVE   (cs_governor.gov)
0329
0330 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
0331 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
0332         "Low Latency Frequency Transition capable processors "
0333         "optimised for use in a battery environment");
0334 MODULE_LICENSE("GPL");
0335
0336 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
0337 struct cpufreq_governor *cpufreq_default_governor(void)
0338 {
0339     return &CPU_FREQ_GOV_CONSERVATIVE;
0340 }
0341 #endif
0342
0343 cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
0344 cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);