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,
115 					CPUFREQ_RELATION_HE);
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,
139 					CPUFREQ_RELATION_LE);
140 		dbs_info->requested_freq = requested_freq;
141 	}
142 
143  out:
144 	return dbs_data->sampling_rate;
145 }
146 
147 /************************** sysfs interface ************************/
148 
149 static ssize_t store_sampling_down_factor(struct gov_attr_set *attr_set,
150 					  const char *buf, size_t count)
151 {
152 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
153 	unsigned int input;
154 	int ret;
155 	ret = sscanf(buf, "%u", &input);
156 
157 	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
158 		return -EINVAL;
159 
160 	dbs_data->sampling_down_factor = input;
161 	return count;
162 }
163 
164 static ssize_t store_up_threshold(struct gov_attr_set *attr_set,
165 				  const char *buf, size_t count)
166 {
167 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
168 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
169 	unsigned int input;
170 	int ret;
171 	ret = sscanf(buf, "%u", &input);
172 
173 	if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
174 		return -EINVAL;
175 
176 	dbs_data->up_threshold = input;
177 	return count;
178 }
179 
180 static ssize_t store_down_threshold(struct gov_attr_set *attr_set,
181 				    const char *buf, size_t count)
182 {
183 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
184 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
185 	unsigned int input;
186 	int ret;
187 	ret = sscanf(buf, "%u", &input);
188 
189 	/* cannot be lower than 1 otherwise freq will not fall */
190 	if (ret != 1 || input < 1 || input > 100 ||
191 			input >= dbs_data->up_threshold)
192 		return -EINVAL;
193 
194 	cs_tuners->down_threshold = input;
195 	return count;
196 }
197 
198 static ssize_t store_ignore_nice_load(struct gov_attr_set *attr_set,
199 				      const char *buf, size_t count)
200 {
201 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
202 	unsigned int input;
203 	int ret;
204 
205 	ret = sscanf(buf, "%u", &input);
206 	if (ret != 1)
207 		return -EINVAL;
208 
209 	if (input > 1)
210 		input = 1;
211 
212 	if (input == dbs_data->ignore_nice_load) /* nothing to do */
213 		return count;
214 
215 	dbs_data->ignore_nice_load = input;
216 
217 	/* we need to re-evaluate prev_cpu_idle */
218 	gov_update_cpu_data(dbs_data);
219 
220 	return count;
221 }
222 
223 static ssize_t store_freq_step(struct gov_attr_set *attr_set, const char *buf,
224 			       size_t count)
225 {
226 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
227 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
228 	unsigned int input;
229 	int ret;
230 	ret = sscanf(buf, "%u", &input);
231 
232 	if (ret != 1)
233 		return -EINVAL;
234 
235 	if (input > 100)
236 		input = 100;
237 
238 	/*
239 	 * no need to test here if freq_step is zero as the user might actually
240 	 * want this, they would be crazy though :)
241 	 */
242 	cs_tuners->freq_step = input;
243 	return count;
244 }
245 
246 gov_show_one_common(sampling_rate);
247 gov_show_one_common(sampling_down_factor);
248 gov_show_one_common(up_threshold);
249 gov_show_one_common(ignore_nice_load);
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_rw(down_threshold);
258 gov_attr_rw(freq_step);
259 
260 static struct attribute *cs_attrs[] = {
261 	&sampling_rate.attr,
262 	&sampling_down_factor.attr,
263 	&up_threshold.attr,
264 	&down_threshold.attr,
265 	&ignore_nice_load.attr,
266 	&freq_step.attr,
267 	NULL
268 };
269 ATTRIBUTE_GROUPS(cs);
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_groups = cs_groups },
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 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
331 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
332 		"Low Latency Frequency Transition capable processors "
333 		"optimised for use in a battery environment");
334 MODULE_LICENSE("GPL");
335 
336 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
337 struct cpufreq_governor *cpufreq_default_governor(void)
338 {
339 	return &CPU_FREQ_GOV_CONSERVATIVE;
340 }
341 #endif
342 
343 cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
344 cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);
345