driver.c

  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#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		 * Warn if the exit latency of a CPU idle state exceeds its
201		 * target residency which is assumed to never happen in cpuidle
202		 * in multiple places.
203		 */
204		if (s->exit_latency_ns > s->target_residency_ns)
205			pr_warn("Idle state %d target residency too low\n", i);
206	}
207}
208
209/**
210 * __cpuidle_register_driver: register the driver
211 * @drv: a valid pointer to a struct cpuidle_driver
212 *
213 * Do some sanity checks, initialize the driver, assign the driver to the
214 * global cpuidle driver variable(s) and set up the broadcast timer if the
215 * cpuidle driver has some states that shut down the local timer.
216 *
217 * Returns 0 on success, a negative error code otherwise:
218 *  * -EINVAL if the driver pointer is NULL or no idle states are available
219 *  * -ENODEV if the cpuidle framework is disabled
220 *  * -EBUSY if the driver is already assigned to the global variable(s)
221 */
222static int __cpuidle_register_driver(struct cpuidle_driver *drv)
223{
224	int ret;
225
226	if (!drv || !drv->state_count)
227		return -EINVAL;
228
229	ret = cpuidle_coupled_state_verify(drv);
230	if (ret)
231		return ret;
232
233	if (cpuidle_disabled())
234		return -ENODEV;
235
236	__cpuidle_driver_init(drv);
237
238	ret = __cpuidle_set_driver(drv);
239	if (ret)
240		return ret;
241
242	if (drv->bctimer)
243		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
244				 (void *)1, 1);
245
246	return 0;
247}
248
249/**
250 * __cpuidle_unregister_driver - unregister the driver
251 * @drv: a valid pointer to a struct cpuidle_driver
252 *
253 * Check if the driver is no longer in use, reset the global cpuidle driver
254 * variable(s) and disable the timer broadcast notification mechanism if it was
255 * in use.
256 *
257 */
258static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
259{
260	if (drv->bctimer) {
261		drv->bctimer = 0;
262		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
263				 NULL, 1);
264	}
265
266	__cpuidle_unset_driver(drv);
267}
268
269/**
270 * cpuidle_register_driver - registers a driver
271 * @drv: a pointer to a valid struct cpuidle_driver
272 *
273 * Register the driver under a lock to prevent concurrent attempts to
274 * [un]register the driver from occurring at the same time.
275 *
276 * Returns 0 on success, a negative error code (returned by
277 * __cpuidle_register_driver()) otherwise.
278 */
279int cpuidle_register_driver(struct cpuidle_driver *drv)
280{
281	struct cpuidle_governor *gov;
282	int ret;
283
284	spin_lock(&cpuidle_driver_lock);
285	ret = __cpuidle_register_driver(drv);
286	spin_unlock(&cpuidle_driver_lock);
287
288	if (!ret && !strlen(param_governor) && drv->governor &&
289	    (cpuidle_get_driver() == drv)) {
290		mutex_lock(&cpuidle_lock);
291		gov = cpuidle_find_governor(drv->governor);
292		if (gov) {
293			cpuidle_prev_governor = cpuidle_curr_governor;
294			if (cpuidle_switch_governor(gov) < 0)
295				cpuidle_prev_governor = NULL;
296		}
297		mutex_unlock(&cpuidle_lock);
298	}
299
300	return ret;
301}
302EXPORT_SYMBOL_GPL(cpuidle_register_driver);
303
304/**
305 * cpuidle_unregister_driver - unregisters a driver
306 * @drv: a pointer to a valid struct cpuidle_driver
307 *
308 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
309 * to [un]register the driver from occurring at the same time.  @drv has to
310 * match the currently registered driver.
311 */
312void cpuidle_unregister_driver(struct cpuidle_driver *drv)
313{
314	bool enabled = (cpuidle_get_driver() == drv);
315
316	spin_lock(&cpuidle_driver_lock);
317	__cpuidle_unregister_driver(drv);
318	spin_unlock(&cpuidle_driver_lock);
319
320	if (!enabled)
321		return;
322
323	mutex_lock(&cpuidle_lock);
324	if (cpuidle_prev_governor) {
325		if (!cpuidle_switch_governor(cpuidle_prev_governor))
326			cpuidle_prev_governor = NULL;
327	}
328	mutex_unlock(&cpuidle_lock);
329}
330EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
331
332/**
333 * cpuidle_get_driver - return the driver tied to the current CPU.
334 *
335 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
336 */
337struct cpuidle_driver *cpuidle_get_driver(void)
338{
339	struct cpuidle_driver *drv;
340	int cpu;
341
342	cpu = get_cpu();
343	drv = __cpuidle_get_cpu_driver(cpu);
344	put_cpu();
345
346	return drv;
347}
348EXPORT_SYMBOL_GPL(cpuidle_get_driver);
349
350/**
351 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
352 * @dev: a valid pointer to a struct cpuidle_device
353 *
354 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
355 * for the CPU associated with @dev.
356 */
357struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
358{
359	if (!dev)
360		return NULL;
361
362	return __cpuidle_get_cpu_driver(dev->cpu);
363}
364EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
365
366/**
367 * cpuidle_driver_state_disabled - Disable or enable an idle state
368 * @drv: cpuidle driver owning the state
369 * @idx: State index
370 * @disable: Whether or not to disable the state
371 */
372void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
373				 bool disable)
374{
375	unsigned int cpu;
376
377	mutex_lock(&cpuidle_lock);
378
379	spin_lock(&cpuidle_driver_lock);
380
381	if (!drv->cpumask) {
382		drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
383		goto unlock;
384	}
385
386	for_each_cpu(cpu, drv->cpumask) {
387		struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
388
389		if (!dev)
390			continue;
391
392		if (disable)
393			dev->states_usage[idx].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
394		else
395			dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
396	}
397
398unlock:
399	spin_unlock(&cpuidle_driver_lock);
400
401	mutex_unlock(&cpuidle_lock);
402}