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