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
18#include "cpuidle.h"
19
20DEFINE_SPINLOCK(cpuidle_driver_lock);
21
22#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
23
24static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
25
26/**
27 * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
28 * @cpu: the CPU handled by the driver
29 *
30 * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
31 * registered for @cpu.
32 */
33static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
34{
35	return per_cpu(cpuidle_drivers, cpu);
36}
37
38/**
39 * __cpuidle_unset_driver - unset per CPU driver variables.
40 * @drv: a valid pointer to a struct cpuidle_driver
41 *
42 * For each CPU in the driver's CPU mask, unset the registered driver per CPU
43 * variable. If @drv is different from the registered driver, the corresponding
44 * variable is not cleared.
45 */
46static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
47{
48	int cpu;
49
50	for_each_cpu(cpu, drv->cpumask) {
51
52		if (drv != __cpuidle_get_cpu_driver(cpu))
53			continue;
54
55		per_cpu(cpuidle_drivers, cpu) = NULL;
56	}
57}
58
59/**
60 * __cpuidle_set_driver - set per CPU driver variables for the given driver.
61 * @drv: a valid pointer to a struct cpuidle_driver
62 *
63 * For each CPU in the driver's cpumask, unset the registered driver per CPU
64 * to @drv.
65 *
66 * Returns 0 on success, -EBUSY if the CPUs have driver(s) 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
74		if (__cpuidle_get_cpu_driver(cpu)) {
75			__cpuidle_unset_driver(drv);
76			return -EBUSY;
77		}
78
79		per_cpu(cpuidle_drivers, cpu) = drv;
80	}
81
82	return 0;
83}
84
85#else
86
87static struct cpuidle_driver *cpuidle_curr_driver;
88
89/**
90 * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
91 * @cpu: ignored without the multiple driver support
92 *
93 * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
94 * previously registered.
95 */
96static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
97{
98	return cpuidle_curr_driver;
99}
100
101/**
102 * __cpuidle_set_driver - assign the global cpuidle driver variable.
103 * @drv: pointer to a struct cpuidle_driver object
104 *
105 * Returns 0 on success, -EBUSY if the driver is already registered.
106 */
107static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
108{
109	if (cpuidle_curr_driver)
110		return -EBUSY;
111
112	cpuidle_curr_driver = drv;
113
114	return 0;
115}
116
117/**
118 * __cpuidle_unset_driver - unset the global cpuidle driver variable.
119 * @drv: a pointer to a struct cpuidle_driver
120 *
121 * Reset the global cpuidle variable to NULL.  If @drv does not match the
122 * registered driver, do nothing.
123 */
124static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
125{
126	if (drv == cpuidle_curr_driver)
127		cpuidle_curr_driver = NULL;
128}
129
130#endif
131
132/**
133 * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
134 * @arg: a void pointer used to match the SMP cross call API
135 *
136 * If @arg is NULL broadcast is disabled otherwise enabled
137 *
138 * This function is executed per CPU by an SMP cross call.  It's not
139 * supposed to be called directly.
140 */
141static void cpuidle_setup_broadcast_timer(void *arg)
142{
143	if (arg)
144		tick_broadcast_enable();
145	else
146		tick_broadcast_disable();
147}
148
149/**
150 * __cpuidle_driver_init - initialize the driver's internal data
151 * @drv: a valid pointer to a struct cpuidle_driver
152 */
153static void __cpuidle_driver_init(struct cpuidle_driver *drv)
154{
155	int i;
156
157	drv->refcnt = 0;
158
159	/*
160	 * Use all possible CPUs as the default, because if the kernel boots
161	 * with some CPUs offline and then we online one of them, the CPU
162	 * notifier has to know which driver to assign.
163	 */
164	if (!drv->cpumask)
165		drv->cpumask = (struct cpumask *)cpu_possible_mask;
166
167	/*
168	 * Look for the timer stop flag in the different states, so that we know
169	 * if the broadcast timer has to be set up.  The loop is in the reverse
170	 * order, because usually one of the deeper states have this flag set.
171	 */
172	for (i = drv->state_count - 1; i >= 0 ; i--) {
173		if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
174			drv->bctimer = 1;
175			break;
176		}
177	}
178}
179
180#ifdef CONFIG_ARCH_HAS_CPU_RELAX
181static int poll_idle(struct cpuidle_device *dev,
182		struct cpuidle_driver *drv, int index)
183{
184	local_irq_enable();
185	if (!current_set_polling_and_test()) {
186		while (!need_resched())
187			cpu_relax();
188	}
189	current_clr_polling();
190
191	return index;
192}
193
194static void poll_idle_init(struct cpuidle_driver *drv)
195{
196	struct cpuidle_state *state = &drv->states[0];
197
198	snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
199	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
200	state->exit_latency = 0;
201	state->target_residency = 0;
202	state->power_usage = -1;
203	state->enter = poll_idle;
204	state->disabled = false;
205}
206#else
207static void poll_idle_init(struct cpuidle_driver *drv) {}
208#endif /* !CONFIG_ARCH_HAS_CPU_RELAX */
209
210/**
211 * __cpuidle_register_driver: register the driver
212 * @drv: a valid pointer to a struct cpuidle_driver
213 *
214 * Do some sanity checks, initialize the driver, assign the driver to the
215 * global cpuidle driver variable(s) and set up the broadcast timer if the
216 * cpuidle driver has some states that shut down the local timer.
217 *
218 * Returns 0 on success, a negative error code otherwise:
219 *  * -EINVAL if the driver pointer is NULL or no idle states are available
220 *  * -ENODEV if the cpuidle framework is disabled
221 *  * -EBUSY if the driver is already assigned to the global variable(s)
222 */
223static int __cpuidle_register_driver(struct cpuidle_driver *drv)
224{
225	int ret;
226
227	if (!drv || !drv->state_count)
228		return -EINVAL;
229
230	if (cpuidle_disabled())
231		return -ENODEV;
232
233	__cpuidle_driver_init(drv);
234
235	ret = __cpuidle_set_driver(drv);
236	if (ret)
237		return ret;
238
239	if (drv->bctimer)
240		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
241				 (void *)1, 1);
242
243	poll_idle_init(drv);
244
245	return 0;
246}
247
248/**
249 * __cpuidle_unregister_driver - unregister the driver
250 * @drv: a valid pointer to a struct cpuidle_driver
251 *
252 * Check if the driver is no longer in use, reset the global cpuidle driver
253 * variable(s) and disable the timer broadcast notification mechanism if it was
254 * in use.
255 *
256 */
257static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
258{
259	if (WARN_ON(drv->refcnt > 0))
260		return;
261
262	if (drv->bctimer) {
263		drv->bctimer = 0;
264		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
265				 NULL, 1);
266	}
267
268	__cpuidle_unset_driver(drv);
269}
270
271/**
272 * cpuidle_register_driver - registers a driver
273 * @drv: a pointer to a valid struct cpuidle_driver
274 *
275 * Register the driver under a lock to prevent concurrent attempts to
276 * [un]register the driver from occuring at the same time.
277 *
278 * Returns 0 on success, a negative error code (returned by
279 * __cpuidle_register_driver()) otherwise.
280 */
281int cpuidle_register_driver(struct cpuidle_driver *drv)
282{
283	int ret;
284
285	spin_lock(&cpuidle_driver_lock);
286	ret = __cpuidle_register_driver(drv);
287	spin_unlock(&cpuidle_driver_lock);
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	spin_lock(&cpuidle_driver_lock);
304	__cpuidle_unregister_driver(drv);
305	spin_unlock(&cpuidle_driver_lock);
306}
307EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
308
309/**
310 * cpuidle_get_driver - return the driver tied to the current CPU.
311 *
312 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
313 */
314struct cpuidle_driver *cpuidle_get_driver(void)
315{
316	struct cpuidle_driver *drv;
317	int cpu;
318
319	cpu = get_cpu();
320	drv = __cpuidle_get_cpu_driver(cpu);
321	put_cpu();
322
323	return drv;
324}
325EXPORT_SYMBOL_GPL(cpuidle_get_driver);
326
327/**
328 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
329 * @dev: a valid pointer to a struct cpuidle_device
330 *
331 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
332 * for the CPU associated with @dev.
333 */
334struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
335{
336	if (!dev)
337		return NULL;
338
339	return __cpuidle_get_cpu_driver(dev->cpu);
340}
341EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
342
343/**
344 * cpuidle_driver_ref - get a reference to the driver.
345 *
346 * Increment the reference counter of the cpuidle driver associated with
347 * the current CPU.
348 *
349 * Returns a pointer to the driver, or NULL if the current CPU has no driver.
350 */
351struct cpuidle_driver *cpuidle_driver_ref(void)
352{
353	struct cpuidle_driver *drv;
354
355	spin_lock(&cpuidle_driver_lock);
356
357	drv = cpuidle_get_driver();
358	if (drv)
359		drv->refcnt++;
360
361	spin_unlock(&cpuidle_driver_lock);
362	return drv;
363}
364
365/**
366 * cpuidle_driver_unref - puts down the refcount for the driver
367 *
368 * Decrement the reference counter of the cpuidle driver associated with
369 * the current CPU.
370 */
371void cpuidle_driver_unref(void)
372{
373	struct cpuidle_driver *drv;
374
375	spin_lock(&cpuidle_driver_lock);
376
377	drv = cpuidle_get_driver();
378	if (drv && !WARN_ON(drv->refcnt <= 0))
379		drv->refcnt--;
380
381	spin_unlock(&cpuidle_driver_lock);
382}
383