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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
22DEFINE_SPINLOCK(cpuidle_driver_lock);
23
24#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
25
26static 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 */
35static 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 */
48static 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 */
68static 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
88static 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 */
97static 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 */
108static 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 */
125static 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 */
142static 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 */
154static void __cpuidle_driver_init(struct cpuidle_driver *drv)
155{
156 int i;
157
158 /*
159 * Use all possible CPUs as the default, because if the kernel boots
160 * with some CPUs offline and then we online one of them, the CPU
161 * notifier has to know which driver to assign.
162 */
163 if (!drv->cpumask)
164 drv->cpumask = (struct cpumask *)cpu_possible_mask;
165
166 for (i = 0; i < drv->state_count; i++) {
167 struct cpuidle_state *s = &drv->states[i];
168
169 /*
170 * Look for the timer stop flag in the different states and if
171 * it is found, indicate that the broadcast timer has to be set
172 * up.
173 */
174 if (s->flags & CPUIDLE_FLAG_TIMER_STOP)
175 drv->bctimer = 1;
176
177 /*
178 * The core will use the target residency and exit latency
179 * values in nanoseconds, but allow drivers to provide them in
180 * microseconds too.
181 */
182 if (s->target_residency > 0)
183 s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
184 else if (s->target_residency_ns < 0)
185 s->target_residency_ns = 0;
186 else
187 s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC);
188
189 if (s->exit_latency > 0)
190 s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC;
191 else if (s->exit_latency_ns < 0)
192 s->exit_latency_ns = 0;
193 else
194 s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
195 }
196}
197
198/**
199 * __cpuidle_register_driver: register the driver
200 * @drv: a valid pointer to a struct cpuidle_driver
201 *
202 * Do some sanity checks, initialize the driver, assign the driver to the
203 * global cpuidle driver variable(s) and set up the broadcast timer if the
204 * cpuidle driver has some states that shut down the local timer.
205 *
206 * Returns 0 on success, a negative error code otherwise:
207 * * -EINVAL if the driver pointer is NULL or no idle states are available
208 * * -ENODEV if the cpuidle framework is disabled
209 * * -EBUSY if the driver is already assigned to the global variable(s)
210 */
211static int __cpuidle_register_driver(struct cpuidle_driver *drv)
212{
213 int ret;
214
215 if (!drv || !drv->state_count)
216 return -EINVAL;
217
218 ret = cpuidle_coupled_state_verify(drv);
219 if (ret)
220 return ret;
221
222 if (cpuidle_disabled())
223 return -ENODEV;
224
225 __cpuidle_driver_init(drv);
226
227 ret = __cpuidle_set_driver(drv);
228 if (ret)
229 return ret;
230
231 if (drv->bctimer)
232 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
233 (void *)1, 1);
234
235 return 0;
236}
237
238/**
239 * __cpuidle_unregister_driver - unregister the driver
240 * @drv: a valid pointer to a struct cpuidle_driver
241 *
242 * Check if the driver is no longer in use, reset the global cpuidle driver
243 * variable(s) and disable the timer broadcast notification mechanism if it was
244 * in use.
245 *
246 */
247static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
248{
249 if (drv->bctimer) {
250 drv->bctimer = 0;
251 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
252 NULL, 1);
253 }
254
255 __cpuidle_unset_driver(drv);
256}
257
258/**
259 * cpuidle_register_driver - registers a driver
260 * @drv: a pointer to a valid struct cpuidle_driver
261 *
262 * Register the driver under a lock to prevent concurrent attempts to
263 * [un]register the driver from occuring at the same time.
264 *
265 * Returns 0 on success, a negative error code (returned by
266 * __cpuidle_register_driver()) otherwise.
267 */
268int cpuidle_register_driver(struct cpuidle_driver *drv)
269{
270 struct cpuidle_governor *gov;
271 int ret;
272
273 spin_lock(&cpuidle_driver_lock);
274 ret = __cpuidle_register_driver(drv);
275 spin_unlock(&cpuidle_driver_lock);
276
277 if (!ret && !strlen(param_governor) && drv->governor &&
278 (cpuidle_get_driver() == drv)) {
279 mutex_lock(&cpuidle_lock);
280 gov = cpuidle_find_governor(drv->governor);
281 if (gov) {
282 cpuidle_prev_governor = cpuidle_curr_governor;
283 if (cpuidle_switch_governor(gov) < 0)
284 cpuidle_prev_governor = NULL;
285 }
286 mutex_unlock(&cpuidle_lock);
287 }
288
289 return ret;
290}
291EXPORT_SYMBOL_GPL(cpuidle_register_driver);
292
293/**
294 * cpuidle_unregister_driver - unregisters a driver
295 * @drv: a pointer to a valid struct cpuidle_driver
296 *
297 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
298 * to [un]register the driver from occuring at the same time. @drv has to
299 * match the currently registered driver.
300 */
301void cpuidle_unregister_driver(struct cpuidle_driver *drv)
302{
303 bool enabled = (cpuidle_get_driver() == drv);
304
305 spin_lock(&cpuidle_driver_lock);
306 __cpuidle_unregister_driver(drv);
307 spin_unlock(&cpuidle_driver_lock);
308
309 if (!enabled)
310 return;
311
312 mutex_lock(&cpuidle_lock);
313 if (cpuidle_prev_governor) {
314 if (!cpuidle_switch_governor(cpuidle_prev_governor))
315 cpuidle_prev_governor = NULL;
316 }
317 mutex_unlock(&cpuidle_lock);
318}
319EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
320
321/**
322 * cpuidle_get_driver - return the driver tied to the current CPU.
323 *
324 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
325 */
326struct cpuidle_driver *cpuidle_get_driver(void)
327{
328 struct cpuidle_driver *drv;
329 int cpu;
330
331 cpu = get_cpu();
332 drv = __cpuidle_get_cpu_driver(cpu);
333 put_cpu();
334
335 return drv;
336}
337EXPORT_SYMBOL_GPL(cpuidle_get_driver);
338
339/**
340 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
341 * @dev: a valid pointer to a struct cpuidle_device
342 *
343 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
344 * for the CPU associated with @dev.
345 */
346struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
347{
348 if (!dev)
349 return NULL;
350
351 return __cpuidle_get_cpu_driver(dev->cpu);
352}
353EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
354
355/**
356 * cpuidle_driver_state_disabled - Disable or enable an idle state
357 * @drv: cpuidle driver owning the state
358 * @idx: State index
359 * @disable: Whether or not to disable the state
360 */
361void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
362 bool disable)
363{
364 unsigned int cpu;
365
366 mutex_lock(&cpuidle_lock);
367
368 spin_lock(&cpuidle_driver_lock);
369
370 if (!drv->cpumask) {
371 drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
372 goto unlock;
373 }
374
375 for_each_cpu(cpu, drv->cpumask) {
376 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
377
378 if (!dev)
379 continue;
380
381 if (disable)
382 dev->states_usage[idx].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
383 else
384 dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
385 }
386
387unlock:
388 spin_unlock(&cpuidle_driver_lock);
389
390 mutex_unlock(&cpuidle_lock);
391}
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/cpuidle.h>
15#include <linux/cpumask.h>
16#include <linux/tick.h>
17#include <linux/cpu.h>
18
19#include "cpuidle.h"
20
21DEFINE_SPINLOCK(cpuidle_driver_lock);
22
23#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
24
25static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
26
27/**
28 * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
29 * @cpu: the CPU handled by the driver
30 *
31 * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
32 * registered for @cpu.
33 */
34static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
35{
36 return per_cpu(cpuidle_drivers, cpu);
37}
38
39/**
40 * __cpuidle_unset_driver - unset per CPU driver variables.
41 * @drv: a valid pointer to a struct cpuidle_driver
42 *
43 * For each CPU in the driver's CPU mask, unset the registered driver per CPU
44 * variable. If @drv is different from the registered driver, the corresponding
45 * variable is not cleared.
46 */
47static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
48{
49 int cpu;
50
51 for_each_cpu(cpu, drv->cpumask) {
52
53 if (drv != __cpuidle_get_cpu_driver(cpu))
54 continue;
55
56 per_cpu(cpuidle_drivers, cpu) = NULL;
57 }
58}
59
60/**
61 * __cpuidle_set_driver - set per CPU driver variables for the given driver.
62 * @drv: a valid pointer to a struct cpuidle_driver
63 *
64 * For each CPU in the driver's cpumask, unset the registered driver per CPU
65 * to @drv.
66 *
67 * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
68 */
69static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
70{
71 int cpu;
72
73 for_each_cpu(cpu, drv->cpumask) {
74
75 if (__cpuidle_get_cpu_driver(cpu)) {
76 __cpuidle_unset_driver(drv);
77 return -EBUSY;
78 }
79
80 per_cpu(cpuidle_drivers, cpu) = drv;
81 }
82
83 return 0;
84}
85
86#else
87
88static 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 */
97static 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 */
108static 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 */
125static 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 */
142static 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 */
154static 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#ifdef CONFIG_ARCH_HAS_CPU_RELAX
182static int __cpuidle poll_idle(struct cpuidle_device *dev,
183 struct cpuidle_driver *drv, int index)
184{
185 local_irq_enable();
186 if (!current_set_polling_and_test()) {
187 while (!need_resched())
188 cpu_relax();
189 }
190 current_clr_polling();
191
192 return index;
193}
194
195static void poll_idle_init(struct cpuidle_driver *drv)
196{
197 struct cpuidle_state *state = &drv->states[0];
198
199 snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
200 snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
201 state->exit_latency = 0;
202 state->target_residency = 0;
203 state->power_usage = -1;
204 state->enter = poll_idle;
205 state->disabled = false;
206}
207#else
208static void poll_idle_init(struct cpuidle_driver *drv) {}
209#endif /* !CONFIG_ARCH_HAS_CPU_RELAX */
210
211/**
212 * __cpuidle_register_driver: register the driver
213 * @drv: a valid pointer to a struct cpuidle_driver
214 *
215 * Do some sanity checks, initialize the driver, assign the driver to the
216 * global cpuidle driver variable(s) and set up the broadcast timer if the
217 * cpuidle driver has some states that shut down the local timer.
218 *
219 * Returns 0 on success, a negative error code otherwise:
220 * * -EINVAL if the driver pointer is NULL or no idle states are available
221 * * -ENODEV if the cpuidle framework is disabled
222 * * -EBUSY if the driver is already assigned to the global variable(s)
223 */
224static int __cpuidle_register_driver(struct cpuidle_driver *drv)
225{
226 int ret;
227
228 if (!drv || !drv->state_count)
229 return -EINVAL;
230
231 ret = cpuidle_coupled_state_verify(drv);
232 if (ret)
233 return ret;
234
235 if (cpuidle_disabled())
236 return -ENODEV;
237
238 __cpuidle_driver_init(drv);
239
240 ret = __cpuidle_set_driver(drv);
241 if (ret)
242 return ret;
243
244 if (drv->bctimer)
245 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
246 (void *)1, 1);
247
248 poll_idle_init(drv);
249
250 return 0;
251}
252
253/**
254 * __cpuidle_unregister_driver - unregister the driver
255 * @drv: a valid pointer to a struct cpuidle_driver
256 *
257 * Check if the driver is no longer in use, reset the global cpuidle driver
258 * variable(s) and disable the timer broadcast notification mechanism if it was
259 * in use.
260 *
261 */
262static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
263{
264 if (WARN_ON(drv->refcnt > 0))
265 return;
266
267 if (drv->bctimer) {
268 drv->bctimer = 0;
269 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
270 NULL, 1);
271 }
272
273 __cpuidle_unset_driver(drv);
274}
275
276/**
277 * cpuidle_register_driver - registers a driver
278 * @drv: a pointer to a valid struct cpuidle_driver
279 *
280 * Register the driver under a lock to prevent concurrent attempts to
281 * [un]register the driver from occuring at the same time.
282 *
283 * Returns 0 on success, a negative error code (returned by
284 * __cpuidle_register_driver()) otherwise.
285 */
286int cpuidle_register_driver(struct cpuidle_driver *drv)
287{
288 int ret;
289
290 spin_lock(&cpuidle_driver_lock);
291 ret = __cpuidle_register_driver(drv);
292 spin_unlock(&cpuidle_driver_lock);
293
294 return ret;
295}
296EXPORT_SYMBOL_GPL(cpuidle_register_driver);
297
298/**
299 * cpuidle_unregister_driver - unregisters a driver
300 * @drv: a pointer to a valid struct cpuidle_driver
301 *
302 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
303 * to [un]register the driver from occuring at the same time. @drv has to
304 * match the currently registered driver.
305 */
306void cpuidle_unregister_driver(struct cpuidle_driver *drv)
307{
308 spin_lock(&cpuidle_driver_lock);
309 __cpuidle_unregister_driver(drv);
310 spin_unlock(&cpuidle_driver_lock);
311}
312EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
313
314/**
315 * cpuidle_get_driver - return the driver tied to the current CPU.
316 *
317 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
318 */
319struct cpuidle_driver *cpuidle_get_driver(void)
320{
321 struct cpuidle_driver *drv;
322 int cpu;
323
324 cpu = get_cpu();
325 drv = __cpuidle_get_cpu_driver(cpu);
326 put_cpu();
327
328 return drv;
329}
330EXPORT_SYMBOL_GPL(cpuidle_get_driver);
331
332/**
333 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
334 * @dev: a valid pointer to a struct cpuidle_device
335 *
336 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
337 * for the CPU associated with @dev.
338 */
339struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
340{
341 if (!dev)
342 return NULL;
343
344 return __cpuidle_get_cpu_driver(dev->cpu);
345}
346EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
347
348/**
349 * cpuidle_driver_ref - get a reference to the driver.
350 *
351 * Increment the reference counter of the cpuidle driver associated with
352 * the current CPU.
353 *
354 * Returns a pointer to the driver, or NULL if the current CPU has no driver.
355 */
356struct cpuidle_driver *cpuidle_driver_ref(void)
357{
358 struct cpuidle_driver *drv;
359
360 spin_lock(&cpuidle_driver_lock);
361
362 drv = cpuidle_get_driver();
363 if (drv)
364 drv->refcnt++;
365
366 spin_unlock(&cpuidle_driver_lock);
367 return drv;
368}
369
370/**
371 * cpuidle_driver_unref - puts down the refcount for the driver
372 *
373 * Decrement the reference counter of the cpuidle driver associated with
374 * the current CPU.
375 */
376void cpuidle_driver_unref(void)
377{
378 struct cpuidle_driver *drv;
379
380 spin_lock(&cpuidle_driver_lock);
381
382 drv = cpuidle_get_driver();
383 if (drv && !WARN_ON(drv->refcnt <= 0))
384 drv->refcnt--;
385
386 spin_unlock(&cpuidle_driver_lock);
387}