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,
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
149static ssize_t sampling_down_factor_store(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
164static ssize_t up_threshold_store(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
180static ssize_t down_threshold_store(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 >= dbs_data->up_threshold)
191		return -EINVAL;
192
193	cs_tuners->down_threshold = input;
194	return count;
195}
196
197static ssize_t ignore_nice_load_store(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
222static ssize_t freq_step_store(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
245gov_show_one_common(sampling_rate);
246gov_show_one_common(sampling_down_factor);
247gov_show_one_common(up_threshold);
248gov_show_one_common(ignore_nice_load);
249gov_show_one(cs, down_threshold);
250gov_show_one(cs, freq_step);
251
252gov_attr_rw(sampling_rate);
253gov_attr_rw(sampling_down_factor);
254gov_attr_rw(up_threshold);
255gov_attr_rw(ignore_nice_load);
256gov_attr_rw(down_threshold);
257gov_attr_rw(freq_step);
258
259static struct attribute *cs_attrs[] = {
260	&sampling_rate.attr,
261	&sampling_down_factor.attr,
262	&up_threshold.attr,
263	&down_threshold.attr,
264	&ignore_nice_load.attr,
265	&freq_step.attr,
266	NULL
267};
268ATTRIBUTE_GROUPS(cs);
269
270/************************** sysfs end ************************/
271
272static struct policy_dbs_info *cs_alloc(void)
273{
274	struct cs_policy_dbs_info *dbs_info;
275
276	dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
277	return dbs_info ? &dbs_info->policy_dbs : NULL;
278}
279
280static void cs_free(struct policy_dbs_info *policy_dbs)
281{
282	kfree(to_dbs_info(policy_dbs));
283}
284
285static int cs_init(struct dbs_data *dbs_data)
286{
287	struct cs_dbs_tuners *tuners;
288
289	tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
290	if (!tuners)
291		return -ENOMEM;
292
293	tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
294	tuners->freq_step = DEF_FREQUENCY_STEP;
295	dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
296	dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
297	dbs_data->ignore_nice_load = 0;
298	dbs_data->tuners = tuners;
299
300	return 0;
301}
302
303static void cs_exit(struct dbs_data *dbs_data)
304{
305	kfree(dbs_data->tuners);
306}
307
308static void cs_start(struct cpufreq_policy *policy)
309{
310	struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
311
312	dbs_info->down_skip = 0;
313	dbs_info->requested_freq = policy->cur;
314}
315
316static struct dbs_governor cs_governor = {
317	.gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
318	.kobj_type = { .default_groups = cs_groups },
319	.gov_dbs_update = cs_dbs_update,
320	.alloc = cs_alloc,
321	.free = cs_free,
322	.init = cs_init,
323	.exit = cs_exit,
324	.start = cs_start,
325};
326
327#define CPU_FREQ_GOV_CONSERVATIVE	(cs_governor.gov)
328
329MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
330MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
331		"Low Latency Frequency Transition capable processors "
332		"optimised for use in a battery environment");
333MODULE_LICENSE("GPL");
334
335#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
336struct cpufreq_governor *cpufreq_default_governor(void)
337{
338	return &CPU_FREQ_GOV_CONSERVATIVE;
339}
340#endif
341
342cpufreq_governor_init(CPU_FREQ_GOV_CONSERVATIVE);
343cpufreq_governor_exit(CPU_FREQ_GOV_CONSERVATIVE);
344