1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6 
7 #ifndef INTEL_WAKEREF_H
8 #define INTEL_WAKEREF_H
9 
10 #include <linux/atomic.h>
11 #include <linux/bitfield.h>
12 #include <linux/bits.h>
13 #include <linux/lockdep.h>
14 #include <linux/mutex.h>
15 #include <linux/refcount.h>
16 #include <linux/stackdepot.h>
17 #include <linux/timer.h>
18 #include <linux/workqueue.h>
19 
20 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG)
21 #define INTEL_WAKEREF_BUG_ON(expr) BUG_ON(expr)
22 #else
23 #define INTEL_WAKEREF_BUG_ON(expr) BUILD_BUG_ON_INVALID(expr)
24 #endif
25 
26 struct intel_runtime_pm;
27 struct intel_wakeref;
28 
29 typedef depot_stack_handle_t intel_wakeref_t;
30 
31 struct intel_wakeref_ops {
32 	int (*get)(struct intel_wakeref *wf);
33 	int (*put)(struct intel_wakeref *wf);
34 };
35 
36 struct intel_wakeref {
37 	atomic_t count;
38 	struct mutex mutex;
39 
40 	intel_wakeref_t wakeref;
41 
42 	struct intel_runtime_pm *rpm;
43 	const struct intel_wakeref_ops *ops;
44 
45 	struct delayed_work work;
46 };
47 
48 struct intel_wakeref_lockclass {
49 	struct lock_class_key mutex;
50 	struct lock_class_key work;
51 };
52 
53 void __intel_wakeref_init(struct intel_wakeref *wf,
54 			  struct intel_runtime_pm *rpm,
55 			  const struct intel_wakeref_ops *ops,
56 			  struct intel_wakeref_lockclass *key);
57 #define intel_wakeref_init(wf, rpm, ops) do {				\
58 	static struct intel_wakeref_lockclass __key;			\
59 									\
60 	__intel_wakeref_init((wf), (rpm), (ops), &__key);		\
61 } while (0)
62 
63 int __intel_wakeref_get_first(struct intel_wakeref *wf);
64 void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags);
65 
66 /**
67  * intel_wakeref_get: Acquire the wakeref
68  * @wf: the wakeref
69  *
70  * Acquire a hold on the wakeref. The first user to do so, will acquire
71  * the runtime pm wakeref and then call the intel_wakeref_ops->get()
72  * underneath the wakeref mutex.
73  *
74  * Note that intel_wakeref_ops->get() is allowed to fail, in which case
75  * the runtime-pm wakeref will be released and the acquisition unwound,
76  * and an error reported.
77  *
78  * Returns: 0 if the wakeref was acquired successfully, or a negative error
79  * code otherwise.
80  */
81 static inline int
82 intel_wakeref_get(struct intel_wakeref *wf)
83 {
84 	might_sleep();
85 	if (unlikely(!atomic_inc_not_zero(&wf->count)))
86 		return __intel_wakeref_get_first(wf);
87 
88 	return 0;
89 }
90 
91 /**
92  * __intel_wakeref_get: Acquire the wakeref, again
93  * @wf: the wakeref
94  *
95  * Increment the wakeref counter, only valid if it is already held by
96  * the caller.
97  *
98  * See intel_wakeref_get().
99  */
100 static inline void
101 __intel_wakeref_get(struct intel_wakeref *wf)
102 {
103 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
104 	atomic_inc(&wf->count);
105 }
106 
107 /**
108  * intel_wakeref_get_if_in_use: Acquire the wakeref
109  * @wf: the wakeref
110  *
111  * Acquire a hold on the wakeref, but only if the wakeref is already
112  * active.
113  *
114  * Returns: true if the wakeref was acquired, false otherwise.
115  */
116 static inline bool
117 intel_wakeref_get_if_active(struct intel_wakeref *wf)
118 {
119 	return atomic_inc_not_zero(&wf->count);
120 }
121 
122 enum {
123 	INTEL_WAKEREF_PUT_ASYNC_BIT = 0,
124 	__INTEL_WAKEREF_PUT_LAST_BIT__
125 };
126 
127 static inline void
128 intel_wakeref_might_get(struct intel_wakeref *wf)
129 {
130 	might_lock(&wf->mutex);
131 }
132 
133 /**
134  * __intel_wakeref_put: Release the wakeref
135  * @wf: the wakeref
136  * @flags: control flags
137  *
138  * Release our hold on the wakeref. When there are no more users,
139  * the runtime pm wakeref will be released after the intel_wakeref_ops->put()
140  * callback is called underneath the wakeref mutex.
141  *
142  * Note that intel_wakeref_ops->put() is allowed to fail, in which case the
143  * runtime-pm wakeref is retained.
144  *
145  */
146 static inline void
147 __intel_wakeref_put(struct intel_wakeref *wf, unsigned long flags)
148 #define INTEL_WAKEREF_PUT_ASYNC BIT(INTEL_WAKEREF_PUT_ASYNC_BIT)
149 #define INTEL_WAKEREF_PUT_DELAY \
150 	GENMASK(BITS_PER_LONG - 1, __INTEL_WAKEREF_PUT_LAST_BIT__)
151 {
152 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
153 	if (unlikely(!atomic_add_unless(&wf->count, -1, 1)))
154 		__intel_wakeref_put_last(wf, flags);
155 }
156 
157 static inline void
158 intel_wakeref_put(struct intel_wakeref *wf)
159 {
160 	might_sleep();
161 	__intel_wakeref_put(wf, 0);
162 }
163 
164 static inline void
165 intel_wakeref_put_async(struct intel_wakeref *wf)
166 {
167 	__intel_wakeref_put(wf, INTEL_WAKEREF_PUT_ASYNC);
168 }
169 
170 static inline void
171 intel_wakeref_put_delay(struct intel_wakeref *wf, unsigned long delay)
172 {
173 	__intel_wakeref_put(wf,
174 			    INTEL_WAKEREF_PUT_ASYNC |
175 			    FIELD_PREP(INTEL_WAKEREF_PUT_DELAY, delay));
176 }
177 
178 static inline void
179 intel_wakeref_might_put(struct intel_wakeref *wf)
180 {
181 	might_lock(&wf->mutex);
182 }
183 
184 /**
185  * intel_wakeref_lock: Lock the wakeref (mutex)
186  * @wf: the wakeref
187  *
188  * Locks the wakeref to prevent it being acquired or released. New users
189  * can still adjust the counter, but the wakeref itself (and callback)
190  * cannot be acquired or released.
191  */
192 static inline void
193 intel_wakeref_lock(struct intel_wakeref *wf)
194 	__acquires(wf->mutex)
195 {
196 	mutex_lock(&wf->mutex);
197 }
198 
199 /**
200  * intel_wakeref_unlock: Unlock the wakeref
201  * @wf: the wakeref
202  *
203  * Releases a previously acquired intel_wakeref_lock().
204  */
205 static inline void
206 intel_wakeref_unlock(struct intel_wakeref *wf)
207 	__releases(wf->mutex)
208 {
209 	mutex_unlock(&wf->mutex);
210 }
211 
212 /**
213  * intel_wakeref_unlock_wait: Wait until the active callback is complete
214  * @wf: the wakeref
215  *
216  * Waits for the active callback (under the @wf->mutex or another CPU) is
217  * complete.
218  */
219 static inline void
220 intel_wakeref_unlock_wait(struct intel_wakeref *wf)
221 {
222 	mutex_lock(&wf->mutex);
223 	mutex_unlock(&wf->mutex);
224 	flush_delayed_work(&wf->work);
225 }
226 
227 /**
228  * intel_wakeref_is_active: Query whether the wakeref is currently held
229  * @wf: the wakeref
230  *
231  * Returns: true if the wakeref is currently held.
232  */
233 static inline bool
234 intel_wakeref_is_active(const struct intel_wakeref *wf)
235 {
236 	return READ_ONCE(wf->wakeref);
237 }
238 
239 /**
240  * __intel_wakeref_defer_park: Defer the current park callback
241  * @wf: the wakeref
242  */
243 static inline void
244 __intel_wakeref_defer_park(struct intel_wakeref *wf)
245 {
246 	lockdep_assert_held(&wf->mutex);
247 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count));
248 	atomic_set_release(&wf->count, 1);
249 }
250 
251 /**
252  * intel_wakeref_wait_for_idle: Wait until the wakeref is idle
253  * @wf: the wakeref
254  *
255  * Wait for the earlier asynchronous release of the wakeref. Note
256  * this will wait for any third party as well, so make sure you only wait
257  * when you have control over the wakeref and trust no one else is acquiring
258  * it.
259  *
260  * Return: 0 on success, error code if killed.
261  */
262 int intel_wakeref_wait_for_idle(struct intel_wakeref *wf);
263 
264 struct intel_wakeref_auto {
265 	struct intel_runtime_pm *rpm;
266 	struct timer_list timer;
267 	intel_wakeref_t wakeref;
268 	spinlock_t lock;
269 	refcount_t count;
270 };
271 
272 /**
273  * intel_wakeref_auto: Delay the runtime-pm autosuspend
274  * @wf: the wakeref
275  * @timeout: relative timeout in jiffies
276  *
277  * The runtime-pm core uses a suspend delay after the last wakeref
278  * is released before triggering runtime suspend of the device. That
279  * delay is configurable via sysfs with little regard to the device
280  * characteristics. Instead, we want to tune the autosuspend based on our
281  * HW knowledge. intel_wakeref_auto() delays the sleep by the supplied
282  * timeout.
283  *
284  * Pass @timeout = 0 to cancel a previous autosuspend by executing the
285  * suspend immediately.
286  */
287 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout);
288 
289 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
290 			     struct intel_runtime_pm *rpm);
291 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf);
292 
293 #endif /* INTEL_WAKEREF_H */
294