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
14struct cs_policy_dbs_info {
15	struct policy_dbs_info policy_dbs;
16	unsigned int down_skip;
17	unsigned int requested_freq;
18};
19
20static 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
25struct 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
37static 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 */
58static 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
147static 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
162static 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
178static 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
196static 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
221static 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
244gov_show_one_common(sampling_rate);
245gov_show_one_common(sampling_down_factor);
246gov_show_one_common(up_threshold);
247gov_show_one_common(ignore_nice_load);
248gov_show_one(cs, down_threshold);
249gov_show_one(cs, freq_step);
250
251gov_attr_rw(sampling_rate);
252gov_attr_rw(sampling_down_factor);
253gov_attr_rw(up_threshold);
254gov_attr_rw(ignore_nice_load);
255gov_attr_rw(down_threshold);
256gov_attr_rw(freq_step);
257
258static 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
270static 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
278static void cs_free(struct policy_dbs_info *policy_dbs)
279{
280	kfree(to_dbs_info(policy_dbs));
281}
282
283static 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
301static void cs_exit(struct dbs_data *dbs_data)
302{
303	kfree(dbs_data->tuners);
304}
305
306static 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
314static 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
327MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
328MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
329		"Low Latency Frequency Transition capable processors "
330		"optimised for use in a battery environment");
331MODULE_LICENSE("GPL");
332
333#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
334struct cpufreq_governor *cpufreq_default_governor(void)
335{
336	return &CPU_FREQ_GOV_CONSERVATIVE;
337}
338#endif
339
340cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
341cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);
342