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1/*
2 * driver.c - driver support
3 *
4 * (C) 2006-2007 Venkatesh Pallipadi <[email protected]>
5 * Shaohua Li <[email protected]>
6 * Adam Belay <[email protected]>
7 *
8 * This code is licenced under the GPL.
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/mutex.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/sched/idle.h>
17#include <linux/cpuidle.h>
18#include <linux/cpumask.h>
19#include <linux/tick.h>
20#include <linux/cpu.h>
21#include <linux/math64.h>
22
23#include "cpuidle.h"
24
25DEFINE_SPINLOCK(cpuidle_driver_lock);
26
27#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
28
29static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
30
31/**
32 * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
33 * @cpu: the CPU handled by the driver
34 *
35 * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
36 * registered for @cpu.
37 */
38static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
39{
40 return per_cpu(cpuidle_drivers, cpu);
41}
42
43/**
44 * __cpuidle_unset_driver - unset per CPU driver variables.
45 * @drv: a valid pointer to a struct cpuidle_driver
46 *
47 * For each CPU in the driver's CPU mask, unset the registered driver per CPU
48 * variable. If @drv is different from the registered driver, the corresponding
49 * variable is not cleared.
50 */
51static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
52{
53 int cpu;
54
55 for_each_cpu(cpu, drv->cpumask) {
56
57 if (drv != __cpuidle_get_cpu_driver(cpu))
58 continue;
59
60 per_cpu(cpuidle_drivers, cpu) = NULL;
61 }
62}
63
64/**
65 * __cpuidle_set_driver - set per CPU driver variables for the given driver.
66 * @drv: a valid pointer to a struct cpuidle_driver
67 *
68 * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
69 * different from drv already.
70 */
71static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
72{
73 int cpu;
74
75 for_each_cpu(cpu, drv->cpumask) {
76 struct cpuidle_driver *old_drv;
77
78 old_drv = __cpuidle_get_cpu_driver(cpu);
79 if (old_drv && old_drv != drv)
80 return -EBUSY;
81 }
82
83 for_each_cpu(cpu, drv->cpumask)
84 per_cpu(cpuidle_drivers, cpu) = drv;
85
86 return 0;
87}
88
89#else
90
91static struct cpuidle_driver *cpuidle_curr_driver;
92
93/**
94 * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
95 * @cpu: ignored without the multiple driver support
96 *
97 * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
98 * previously registered.
99 */
100static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
101{
102 return cpuidle_curr_driver;
103}
104
105/**
106 * __cpuidle_set_driver - assign the global cpuidle driver variable.
107 * @drv: pointer to a struct cpuidle_driver object
108 *
109 * Returns 0 on success, -EBUSY if the driver is already registered.
110 */
111static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
112{
113 if (cpuidle_curr_driver)
114 return -EBUSY;
115
116 cpuidle_curr_driver = drv;
117
118 return 0;
119}
120
121/**
122 * __cpuidle_unset_driver - unset the global cpuidle driver variable.
123 * @drv: a pointer to a struct cpuidle_driver
124 *
125 * Reset the global cpuidle variable to NULL. If @drv does not match the
126 * registered driver, do nothing.
127 */
128static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
129{
130 if (drv == cpuidle_curr_driver)
131 cpuidle_curr_driver = NULL;
132}
133
134#endif
135
136/**
137 * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
138 * @arg: a void pointer used to match the SMP cross call API
139 *
140 * If @arg is NULL broadcast is disabled otherwise enabled
141 *
142 * This function is executed per CPU by an SMP cross call. It's not
143 * supposed to be called directly.
144 */
145static void cpuidle_setup_broadcast_timer(void *arg)
146{
147 if (arg)
148 tick_broadcast_enable();
149 else
150 tick_broadcast_disable();
151}
152
153/**
154 * __cpuidle_driver_init - initialize the driver's internal data
155 * @drv: a valid pointer to a struct cpuidle_driver
156 */
157static void __cpuidle_driver_init(struct cpuidle_driver *drv)
158{
159 int i;
160
161 /*
162 * Use all possible CPUs as the default, because if the kernel boots
163 * with some CPUs offline and then we online one of them, the CPU
164 * notifier has to know which driver to assign.
165 */
166 if (!drv->cpumask)
167 drv->cpumask = (struct cpumask *)cpu_possible_mask;
168
169 for (i = 0; i < drv->state_count; i++) {
170 struct cpuidle_state *s = &drv->states[i];
171
172 /*
173 * Look for the timer stop flag in the different states and if
174 * it is found, indicate that the broadcast timer has to be set
175 * up.
176 */
177 if (s->flags & CPUIDLE_FLAG_TIMER_STOP)
178 drv->bctimer = 1;
179
180 /*
181 * The core will use the target residency and exit latency
182 * values in nanoseconds, but allow drivers to provide them in
183 * microseconds too.
184 */
185 if (s->target_residency > 0)
186 s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
187 else if (s->target_residency_ns < 0)
188 s->target_residency_ns = 0;
189 else
190 s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC);
191
192 if (s->exit_latency > 0)
193 s->exit_latency_ns = mul_u32_u32(s->exit_latency, NSEC_PER_USEC);
194 else if (s->exit_latency_ns < 0)
195 s->exit_latency_ns = 0;
196 else
197 s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
198 }
199}
200
201/**
202 * __cpuidle_register_driver: register the driver
203 * @drv: a valid pointer to a struct cpuidle_driver
204 *
205 * Do some sanity checks, initialize the driver, assign the driver to the
206 * global cpuidle driver variable(s) and set up the broadcast timer if the
207 * cpuidle driver has some states that shut down the local timer.
208 *
209 * Returns 0 on success, a negative error code otherwise:
210 * * -EINVAL if the driver pointer is NULL or no idle states are available
211 * * -ENODEV if the cpuidle framework is disabled
212 * * -EBUSY if the driver is already assigned to the global variable(s)
213 */
214static int __cpuidle_register_driver(struct cpuidle_driver *drv)
215{
216 int ret;
217
218 if (!drv || !drv->state_count)
219 return -EINVAL;
220
221 ret = cpuidle_coupled_state_verify(drv);
222 if (ret)
223 return ret;
224
225 if (cpuidle_disabled())
226 return -ENODEV;
227
228 __cpuidle_driver_init(drv);
229
230 ret = __cpuidle_set_driver(drv);
231 if (ret)
232 return ret;
233
234 if (drv->bctimer)
235 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
236 (void *)1, 1);
237
238 return 0;
239}
240
241/**
242 * __cpuidle_unregister_driver - unregister the driver
243 * @drv: a valid pointer to a struct cpuidle_driver
244 *
245 * Check if the driver is no longer in use, reset the global cpuidle driver
246 * variable(s) and disable the timer broadcast notification mechanism if it was
247 * in use.
248 *
249 */
250static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
251{
252 if (drv->bctimer) {
253 drv->bctimer = 0;
254 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
255 NULL, 1);
256 }
257
258 __cpuidle_unset_driver(drv);
259}
260
261/**
262 * cpuidle_register_driver - registers a driver
263 * @drv: a pointer to a valid struct cpuidle_driver
264 *
265 * Register the driver under a lock to prevent concurrent attempts to
266 * [un]register the driver from occurring at the same time.
267 *
268 * Returns 0 on success, a negative error code (returned by
269 * __cpuidle_register_driver()) otherwise.
270 */
271int cpuidle_register_driver(struct cpuidle_driver *drv)
272{
273 struct cpuidle_governor *gov;
274 int ret;
275
276 spin_lock(&cpuidle_driver_lock);
277 ret = __cpuidle_register_driver(drv);
278 spin_unlock(&cpuidle_driver_lock);
279
280 if (!ret && !strlen(param_governor) && drv->governor &&
281 (cpuidle_get_driver() == drv)) {
282 mutex_lock(&cpuidle_lock);
283 gov = cpuidle_find_governor(drv->governor);
284 if (gov) {
285 cpuidle_prev_governor = cpuidle_curr_governor;
286 if (cpuidle_switch_governor(gov) < 0)
287 cpuidle_prev_governor = NULL;
288 }
289 mutex_unlock(&cpuidle_lock);
290 }
291
292 return ret;
293}
294EXPORT_SYMBOL_GPL(cpuidle_register_driver);
295
296/**
297 * cpuidle_unregister_driver - unregisters a driver
298 * @drv: a pointer to a valid struct cpuidle_driver
299 *
300 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
301 * to [un]register the driver from occurring at the same time. @drv has to
302 * match the currently registered driver.
303 */
304void cpuidle_unregister_driver(struct cpuidle_driver *drv)
305{
306 bool enabled = (cpuidle_get_driver() == drv);
307
308 spin_lock(&cpuidle_driver_lock);
309 __cpuidle_unregister_driver(drv);
310 spin_unlock(&cpuidle_driver_lock);
311
312 if (!enabled)
313 return;
314
315 mutex_lock(&cpuidle_lock);
316 if (cpuidle_prev_governor) {
317 if (!cpuidle_switch_governor(cpuidle_prev_governor))
318 cpuidle_prev_governor = NULL;
319 }
320 mutex_unlock(&cpuidle_lock);
321}
322EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
323
324/**
325 * cpuidle_get_driver - return the driver tied to the current CPU.
326 *
327 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
328 */
329struct cpuidle_driver *cpuidle_get_driver(void)
330{
331 struct cpuidle_driver *drv;
332 int cpu;
333
334 cpu = get_cpu();
335 drv = __cpuidle_get_cpu_driver(cpu);
336 put_cpu();
337
338 return drv;
339}
340EXPORT_SYMBOL_GPL(cpuidle_get_driver);
341
342/**
343 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
344 * @dev: a valid pointer to a struct cpuidle_device
345 *
346 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
347 * for the CPU associated with @dev.
348 */
349struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
350{
351 if (!dev)
352 return NULL;
353
354 return __cpuidle_get_cpu_driver(dev->cpu);
355}
356EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
357
358/**
359 * cpuidle_driver_state_disabled - Disable or enable an idle state
360 * @drv: cpuidle driver owning the state
361 * @idx: State index
362 * @disable: Whether or not to disable the state
363 */
364void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
365 bool disable)
366{
367 unsigned int cpu;
368
369 mutex_lock(&cpuidle_lock);
370
371 spin_lock(&cpuidle_driver_lock);
372
373 if (!drv->cpumask) {
374 drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
375 goto unlock;
376 }
377
378 for_each_cpu(cpu, drv->cpumask) {
379 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
380
381 if (!dev)
382 continue;
383
384 if (disable)
385 dev->states_usage[idx].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
386 else
387 dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
388 }
389
390unlock:
391 spin_unlock(&cpuidle_driver_lock);
392
393 mutex_unlock(&cpuidle_lock);
394}