1 /*
2 * driver.c - driver support
3 *
4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
5 * Shaohua Li <shaohua.li@intel.com>
6 * Adam Belay <abelay@novell.com>
7 *
8 * This code is licenced under the GPL.
9 */
10
11 #include <linux/mutex.h>
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/sched/idle.h>
15 #include <linux/cpuidle.h>
16 #include <linux/cpumask.h>
17 #include <linux/tick.h>
18 #include <linux/cpu.h>
19
20 #include "cpuidle.h"
21
22 DEFINE_SPINLOCK(cpuidle_driver_lock);
23
24 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
25
26 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
27
28 /**
29 * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
30 * @cpu: the CPU handled by the driver
31 *
32 * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
33 * registered for @cpu.
34 */
35 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
36 {
37 return per_cpu(cpuidle_drivers, cpu);
38 }
39
40 /**
41 * __cpuidle_unset_driver - unset per CPU driver variables.
42 * @drv: a valid pointer to a struct cpuidle_driver
43 *
44 * For each CPU in the driver's CPU mask, unset the registered driver per CPU
45 * variable. If @drv is different from the registered driver, the corresponding
46 * variable is not cleared.
47 */
48 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
49 {
50 int cpu;
51
52 for_each_cpu(cpu, drv->cpumask) {
53
54 if (drv != __cpuidle_get_cpu_driver(cpu))
55 continue;
56
57 per_cpu(cpuidle_drivers, cpu) = NULL;
58 }
59 }
60
61 /**
62 * __cpuidle_set_driver - set per CPU driver variables for the given driver.
63 * @drv: a valid pointer to a struct cpuidle_driver
64 *
65 * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
66 * different from drv already.
67 */
68 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
69 {
70 int cpu;
71
72 for_each_cpu(cpu, drv->cpumask) {
73 struct cpuidle_driver *old_drv;
74
75 old_drv = __cpuidle_get_cpu_driver(cpu);
76 if (old_drv && old_drv != drv)
77 return -EBUSY;
78 }
79
80 for_each_cpu(cpu, drv->cpumask)
81 per_cpu(cpuidle_drivers, cpu) = drv;
82
83 return 0;
84 }
85
86 #else
87
88 static struct cpuidle_driver *cpuidle_curr_driver;
89
90 /**
91 * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
92 * @cpu: ignored without the multiple driver support
93 *
94 * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
95 * previously registered.
96 */
97 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
98 {
99 return cpuidle_curr_driver;
100 }
101
102 /**
103 * __cpuidle_set_driver - assign the global cpuidle driver variable.
104 * @drv: pointer to a struct cpuidle_driver object
105 *
106 * Returns 0 on success, -EBUSY if the driver is already registered.
107 */
108 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
109 {
110 if (cpuidle_curr_driver)
111 return -EBUSY;
112
113 cpuidle_curr_driver = drv;
114
115 return 0;
116 }
117
118 /**
119 * __cpuidle_unset_driver - unset the global cpuidle driver variable.
120 * @drv: a pointer to a struct cpuidle_driver
121 *
122 * Reset the global cpuidle variable to NULL. If @drv does not match the
123 * registered driver, do nothing.
124 */
125 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
126 {
127 if (drv == cpuidle_curr_driver)
128 cpuidle_curr_driver = NULL;
129 }
130
131 #endif
132
133 /**
134 * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
135 * @arg: a void pointer used to match the SMP cross call API
136 *
137 * If @arg is NULL broadcast is disabled otherwise enabled
138 *
139 * This function is executed per CPU by an SMP cross call. It's not
140 * supposed to be called directly.
141 */
142 static void cpuidle_setup_broadcast_timer(void *arg)
143 {
144 if (arg)
145 tick_broadcast_enable();
146 else
147 tick_broadcast_disable();
148 }
149
150 /**
151 * __cpuidle_driver_init - initialize the driver's internal data
152 * @drv: a valid pointer to a struct cpuidle_driver
153 */
154 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
155 {
156 int i;
157
158 drv->refcnt = 0;
159
160 /*
161 * Use all possible CPUs as the default, because if the kernel boots
162 * with some CPUs offline and then we online one of them, the CPU
163 * notifier has to know which driver to assign.
164 */
165 if (!drv->cpumask)
166 drv->cpumask = (struct cpumask *)cpu_possible_mask;
167
168 /*
169 * Look for the timer stop flag in the different states, so that we know
170 * if the broadcast timer has to be set up. The loop is in the reverse
171 * order, because usually one of the deeper states have this flag set.
172 */
173 for (i = drv->state_count - 1; i >= 0 ; i--) {
174 if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
175 drv->bctimer = 1;
176 break;
177 }
178 }
179 }
180
181 /**
182 * __cpuidle_register_driver: register the driver
183 * @drv: a valid pointer to a struct cpuidle_driver
184 *
185 * Do some sanity checks, initialize the driver, assign the driver to the
186 * global cpuidle driver variable(s) and set up the broadcast timer if the
187 * cpuidle driver has some states that shut down the local timer.
188 *
189 * Returns 0 on success, a negative error code otherwise:
190 * * -EINVAL if the driver pointer is NULL or no idle states are available
191 * * -ENODEV if the cpuidle framework is disabled
192 * * -EBUSY if the driver is already assigned to the global variable(s)
193 */
194 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
195 {
196 int ret;
197
198 if (!drv || !drv->state_count)
199 return -EINVAL;
200
201 ret = cpuidle_coupled_state_verify(drv);
202 if (ret)
203 return ret;
204
205 if (cpuidle_disabled())
206 return -ENODEV;
207
208 __cpuidle_driver_init(drv);
209
210 ret = __cpuidle_set_driver(drv);
211 if (ret)
212 return ret;
213
214 if (drv->bctimer)
215 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
216 (void *)1, 1);
217
218 return 0;
219 }
220
221 /**
222 * __cpuidle_unregister_driver - unregister the driver
223 * @drv: a valid pointer to a struct cpuidle_driver
224 *
225 * Check if the driver is no longer in use, reset the global cpuidle driver
226 * variable(s) and disable the timer broadcast notification mechanism if it was
227 * in use.
228 *
229 */
230 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
231 {
232 if (WARN_ON(drv->refcnt > 0))
233 return;
234
235 if (drv->bctimer) {
236 drv->bctimer = 0;
237 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
238 NULL, 1);
239 }
240
241 __cpuidle_unset_driver(drv);
242 }
243
244 /**
245 * cpuidle_register_driver - registers a driver
246 * @drv: a pointer to a valid struct cpuidle_driver
247 *
248 * Register the driver under a lock to prevent concurrent attempts to
249 * [un]register the driver from occuring at the same time.
250 *
251 * Returns 0 on success, a negative error code (returned by
252 * __cpuidle_register_driver()) otherwise.
253 */
254 int cpuidle_register_driver(struct cpuidle_driver *drv)
255 {
256 struct cpuidle_governor *gov;
257 int ret;
258
259 spin_lock(&cpuidle_driver_lock);
260 ret = __cpuidle_register_driver(drv);
261 spin_unlock(&cpuidle_driver_lock);
262
263 if (!ret && !strlen(param_governor) && drv->governor &&
264 (cpuidle_get_driver() == drv)) {
265 mutex_lock(&cpuidle_lock);
266 gov = cpuidle_find_governor(drv->governor);
267 if (gov) {
268 cpuidle_prev_governor = cpuidle_curr_governor;
269 if (cpuidle_switch_governor(gov) < 0)
270 cpuidle_prev_governor = NULL;
271 }
272 mutex_unlock(&cpuidle_lock);
273 }
274
275 return ret;
276 }
277 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
278
279 /**
280 * cpuidle_unregister_driver - unregisters a driver
281 * @drv: a pointer to a valid struct cpuidle_driver
282 *
283 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
284 * to [un]register the driver from occuring at the same time. @drv has to
285 * match the currently registered driver.
286 */
287 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
288 {
289 bool enabled = (cpuidle_get_driver() == drv);
290
291 spin_lock(&cpuidle_driver_lock);
292 __cpuidle_unregister_driver(drv);
293 spin_unlock(&cpuidle_driver_lock);
294
295 if (!enabled)
296 return;
297
298 mutex_lock(&cpuidle_lock);
299 if (cpuidle_prev_governor) {
300 if (!cpuidle_switch_governor(cpuidle_prev_governor))
301 cpuidle_prev_governor = NULL;
302 }
303 mutex_unlock(&cpuidle_lock);
304 }
305 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
306
307 /**
308 * cpuidle_get_driver - return the driver tied to the current CPU.
309 *
310 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
311 */
312 struct cpuidle_driver *cpuidle_get_driver(void)
313 {
314 struct cpuidle_driver *drv;
315 int cpu;
316
317 cpu = get_cpu();
318 drv = __cpuidle_get_cpu_driver(cpu);
319 put_cpu();
320
321 return drv;
322 }
323 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
324
325 /**
326 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
327 * @dev: a valid pointer to a struct cpuidle_device
328 *
329 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
330 * for the CPU associated with @dev.
331 */
332 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
333 {
334 if (!dev)
335 return NULL;
336
337 return __cpuidle_get_cpu_driver(dev->cpu);
338 }
339 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
340
341 /**
342 * cpuidle_driver_ref - get a reference to the driver.
343 *
344 * Increment the reference counter of the cpuidle driver associated with
345 * the current CPU.
346 *
347 * Returns a pointer to the driver, or NULL if the current CPU has no driver.
348 */
349 struct cpuidle_driver *cpuidle_driver_ref(void)
350 {
351 struct cpuidle_driver *drv;
352
353 spin_lock(&cpuidle_driver_lock);
354
355 drv = cpuidle_get_driver();
356 if (drv)
357 drv->refcnt++;
358
359 spin_unlock(&cpuidle_driver_lock);
360 return drv;
361 }
362
363 /**
364 * cpuidle_driver_unref - puts down the refcount for the driver
365 *
366 * Decrement the reference counter of the cpuidle driver associated with
367 * the current CPU.
368 */
369 void cpuidle_driver_unref(void)
370 {
371 struct cpuidle_driver *drv;
372
373 spin_lock(&cpuidle_driver_lock);
374
375 drv = cpuidle_get_driver();
376 if (drv && !WARN_ON(drv->refcnt <= 0))
377 drv->refcnt--;
378
379 spin_unlock(&cpuidle_driver_lock);
380 }