1 /*
2  *  drivers/cpufreq/cpufreq_conservative.c
3  *
4  *  Copyright (C)  2001 Russell King
5  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6  *                      Jun Nakajima <jun.nakajima@intel.com>
7  *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  */
13 
14 #include <linux/slab.h>
15 #include "cpufreq_governor.h"
16 
17 struct cs_policy_dbs_info {
18 	struct policy_dbs_info policy_dbs;
19 	unsigned int down_skip;
20 	unsigned int requested_freq;
21 };
22 
23 static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
24 {
25 	return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
26 }
27 
28 /* Conservative governor macros */
29 #define DEF_FREQUENCY_UP_THRESHOLD		(80)
30 #define DEF_FREQUENCY_DOWN_THRESHOLD		(20)
31 #define DEF_FREQUENCY_STEP			(5)
32 #define DEF_SAMPLING_DOWN_FACTOR		(1)
33 #define MAX_SAMPLING_DOWN_FACTOR		(10)
34 
35 static DEFINE_PER_CPU(struct cs_cpu_dbs_info_s, cs_cpu_dbs_info);
36 
37 static struct dbs_governor cs_dbs_gov;
38 
39 static inline unsigned int get_freq_target(struct cs_dbs_tuners *cs_tuners,
40 					   struct cpufreq_policy *policy)
41 {
42 	unsigned int freq_target = (cs_tuners->freq_step * policy->max) / 100;
43 
44 	/* max freq cannot be less than 100. But who knows... */
45 	if (unlikely(freq_target == 0))
46 		freq_target = DEF_FREQUENCY_STEP;
47 
48 	return freq_target;
49 }
50 
51 /*
52  * Every sampling_rate, we check, if current idle time is less than 20%
53  * (default), then we try to increase frequency. Every sampling_rate *
54  * sampling_down_factor, we check, if current idle time is more than 80%
55  * (default), then we try to decrease frequency
56  *
57  * Any frequency increase takes it to the maximum frequency. Frequency reduction
58  * happens at minimum steps of 5% (default) of maximum frequency
59  */
60 static unsigned int cs_dbs_timer(struct cpufreq_policy *policy)
61 {
62 	struct policy_dbs_info *policy_dbs = policy->governor_data;
63 	struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
64 	struct dbs_data *dbs_data = policy_dbs->dbs_data;
65 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
66 	unsigned int load = dbs_update(policy);
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 	/* Check for frequency increase */
76 	if (load > dbs_data->up_threshold) {
77 		dbs_info->down_skip = 0;
78 
79 		/* if we are already at full speed then break out early */
80 		if (dbs_info->requested_freq == policy->max)
81 			goto out;
82 
83 		dbs_info->requested_freq += get_freq_target(cs_tuners, policy);
84 
85 		if (dbs_info->requested_freq > policy->max)
86 			dbs_info->requested_freq = policy->max;
87 
88 		__cpufreq_driver_target(policy, dbs_info->requested_freq,
89 			CPUFREQ_RELATION_H);
90 		goto out;
91 	}
92 
93 	/* if sampling_down_factor is active break out early */
94 	if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
95 		goto out;
96 	dbs_info->down_skip = 0;
97 
98 	/* Check for frequency decrease */
99 	if (load < cs_tuners->down_threshold) {
100 		unsigned int freq_target;
101 		/*
102 		 * if we cannot reduce the frequency anymore, break out early
103 		 */
104 		if (policy->cur == policy->min)
105 			goto out;
106 
107 		freq_target = get_freq_target(cs_tuners, policy);
108 		if (dbs_info->requested_freq > freq_target)
109 			dbs_info->requested_freq -= freq_target;
110 		else
111 			dbs_info->requested_freq = policy->min;
112 
113 		__cpufreq_driver_target(policy, dbs_info->requested_freq,
114 				CPUFREQ_RELATION_L);
115 	}
116 
117  out:
118 	return dbs_data->sampling_rate;
119 }
120 
121 static int dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
122 				void *data);
123 
124 static struct notifier_block cs_cpufreq_notifier_block = {
125 	.notifier_call = dbs_cpufreq_notifier,
126 };
127 
128 /************************** sysfs interface ************************/
129 static struct dbs_governor cs_dbs_gov;
130 
131 static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
132 		const char *buf, size_t count)
133 {
134 	unsigned int input;
135 	int ret;
136 	ret = sscanf(buf, "%u", &input);
137 
138 	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
139 		return -EINVAL;
140 
141 	dbs_data->sampling_down_factor = input;
142 	return count;
143 }
144 
145 static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
146 		size_t count)
147 {
148 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
149 	unsigned int input;
150 	int ret;
151 	ret = sscanf(buf, "%u", &input);
152 
153 	if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
154 		return -EINVAL;
155 
156 	dbs_data->up_threshold = input;
157 	return count;
158 }
159 
160 static ssize_t store_down_threshold(struct dbs_data *dbs_data, const char *buf,
161 		size_t count)
162 {
163 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
164 	unsigned int input;
165 	int ret;
166 	ret = sscanf(buf, "%u", &input);
167 
168 	/* cannot be lower than 11 otherwise freq will not fall */
169 	if (ret != 1 || input < 11 || input > 100 ||
170 			input >= dbs_data->up_threshold)
171 		return -EINVAL;
172 
173 	cs_tuners->down_threshold = input;
174 	return count;
175 }
176 
177 static ssize_t store_ignore_nice_load(struct dbs_data *dbs_data,
178 		const char *buf, size_t count)
179 {
180 	unsigned int input;
181 	int ret;
182 
183 	ret = sscanf(buf, "%u", &input);
184 	if (ret != 1)
185 		return -EINVAL;
186 
187 	if (input > 1)
188 		input = 1;
189 
190 	if (input == dbs_data->ignore_nice_load) /* nothing to do */
191 		return count;
192 
193 	dbs_data->ignore_nice_load = input;
194 
195 	/* we need to re-evaluate prev_cpu_idle */
196 	gov_update_cpu_data(&cs_dbs_gov, dbs_data);
197 
198 	return count;
199 }
200 
201 static ssize_t store_freq_step(struct dbs_data *dbs_data, const char *buf,
202 		size_t count)
203 {
204 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
205 	unsigned int input;
206 	int ret;
207 	ret = sscanf(buf, "%u", &input);
208 
209 	if (ret != 1)
210 		return -EINVAL;
211 
212 	if (input > 100)
213 		input = 100;
214 
215 	/*
216 	 * no need to test here if freq_step is zero as the user might actually
217 	 * want this, they would be crazy though :)
218 	 */
219 	cs_tuners->freq_step = input;
220 	return count;
221 }
222 
223 gov_show_one_common(sampling_rate);
224 gov_show_one_common(sampling_down_factor);
225 gov_show_one_common(up_threshold);
226 gov_show_one_common(ignore_nice_load);
227 gov_show_one_common(min_sampling_rate);
228 gov_show_one(cs, down_threshold);
229 gov_show_one(cs, freq_step);
230 
231 gov_attr_rw(sampling_rate);
232 gov_attr_rw(sampling_down_factor);
233 gov_attr_rw(up_threshold);
234 gov_attr_rw(ignore_nice_load);
235 gov_attr_ro(min_sampling_rate);
236 gov_attr_rw(down_threshold);
237 gov_attr_rw(freq_step);
238 
239 static struct attribute *cs_attributes[] = {
240 	&min_sampling_rate.attr,
241 	&sampling_rate.attr,
242 	&sampling_down_factor.attr,
243 	&up_threshold.attr,
244 	&down_threshold.attr,
245 	&ignore_nice_load.attr,
246 	&freq_step.attr,
247 	NULL
248 };
249 
250 /************************** sysfs end ************************/
251 
252 static struct policy_dbs_info *cs_alloc(void)
253 {
254 	struct cs_policy_dbs_info *dbs_info;
255 
256 	dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
257 	return dbs_info ? &dbs_info->policy_dbs : NULL;
258 }
259 
260 static void cs_free(struct policy_dbs_info *policy_dbs)
261 {
262 	kfree(to_dbs_info(policy_dbs));
263 }
264 
265 static int cs_init(struct dbs_data *dbs_data, bool notify)
266 {
267 	struct cs_dbs_tuners *tuners;
268 
269 	tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
270 	if (!tuners) {
271 		pr_err("%s: kzalloc failed\n", __func__);
272 		return -ENOMEM;
273 	}
274 
275 	tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
276 	tuners->freq_step = DEF_FREQUENCY_STEP;
277 	dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
278 	dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
279 	dbs_data->ignore_nice_load = 0;
280 
281 	dbs_data->tuners = tuners;
282 	dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
283 		jiffies_to_usecs(10);
284 
285 	if (notify)
286 		cpufreq_register_notifier(&cs_cpufreq_notifier_block,
287 					  CPUFREQ_TRANSITION_NOTIFIER);
288 
289 	return 0;
290 }
291 
292 static void cs_exit(struct dbs_data *dbs_data, bool notify)
293 {
294 	if (notify)
295 		cpufreq_unregister_notifier(&cs_cpufreq_notifier_block,
296 					    CPUFREQ_TRANSITION_NOTIFIER);
297 
298 	kfree(dbs_data->tuners);
299 }
300 
301 static void cs_start(struct cpufreq_policy *policy)
302 {
303 	struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
304 
305 	dbs_info->down_skip = 0;
306 	dbs_info->requested_freq = policy->cur;
307 }
308 
309 define_get_cpu_dbs_routines(cs_cpu_dbs_info);
310 
311 static struct dbs_governor cs_dbs_gov = {
312 	.gov = {
313 		.name = "conservative",
314 		.governor = cpufreq_governor_dbs,
315 		.max_transition_latency = TRANSITION_LATENCY_LIMIT,
316 		.owner = THIS_MODULE,
317 	},
318 	.kobj_type = { .default_attrs = cs_attributes },
319 	.get_cpu_cdbs = get_cpu_cdbs,
320 	.gov_dbs_timer = cs_dbs_timer,
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_dbs_gov.gov)
329 
330 static int dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
331 				void *data)
332 {
333 	struct cpufreq_freqs *freq = data;
334 	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(freq->cpu);
335 	struct cs_policy_dbs_info *dbs_info;
336 
337 	if (!policy)
338 		return 0;
339 
340 	/* policy isn't governed by conservative governor */
341 	if (policy->governor != CPU_FREQ_GOV_CONSERVATIVE)
342 		return 0;
343 
344 	dbs_info = to_dbs_info(policy->governor_data);
345 	/*
346 	 * we only care if our internally tracked freq moves outside the 'valid'
347 	 * ranges of frequency available to us otherwise we do not change it
348 	*/
349 	if (dbs_info->requested_freq > policy->max
350 			|| dbs_info->requested_freq < policy->min)
351 		dbs_info->requested_freq = freq->new;
352 
353 	return 0;
354 }
355 
356 static int __init cpufreq_gov_dbs_init(void)
357 {
358 	return cpufreq_register_governor(CPU_FREQ_GOV_CONSERVATIVE);
359 }
360 
361 static void __exit cpufreq_gov_dbs_exit(void)
362 {
363 	cpufreq_unregister_governor(CPU_FREQ_GOV_CONSERVATIVE);
364 }
365 
366 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
367 MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
368 		"Low Latency Frequency Transition capable processors "
369 		"optimised for use in a battery environment");
370 MODULE_LICENSE("GPL");
371 
372 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
373 struct cpufreq_governor *cpufreq_default_governor(void)
374 {
375 	return CPU_FREQ_GOV_CONSERVATIVE;
376 }
377 
378 fs_initcall(cpufreq_gov_dbs_init);
379 #else
380 module_init(cpufreq_gov_dbs_init);
381 #endif
382 module_exit(cpufreq_gov_dbs_exit);
383