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 @fn underneath the wakeref
72  * mutex.
73  *
74  * Note that @fn is allowed to fail, in which case the runtime-pm wakeref
75  * will be released and the acquisition unwound, and an error reported.
76  *
77  * Returns: 0 if the wakeref was acquired successfully, or a negative error
78  * code otherwise.
79  */
80 static inline int
81 intel_wakeref_get(struct intel_wakeref *wf)
82 {
83 	might_sleep();
84 	if (unlikely(!atomic_inc_not_zero(&wf->count)))
85 		return __intel_wakeref_get_first(wf);
86 
87 	return 0;
88 }
89 
90 /**
91  * __intel_wakeref_get: Acquire the wakeref, again
92  * @wf: the wakeref
93  *
94  * Increment the wakeref counter, only valid if it is already held by
95  * the caller.
96  *
97  * See intel_wakeref_get().
98  */
99 static inline void
100 __intel_wakeref_get(struct intel_wakeref *wf)
101 {
102 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
103 	atomic_inc(&wf->count);
104 }
105 
106 /**
107  * intel_wakeref_get_if_in_use: Acquire the wakeref
108  * @wf: the wakeref
109  *
110  * Acquire a hold on the wakeref, but only if the wakeref is already
111  * active.
112  *
113  * Returns: true if the wakeref was acquired, false otherwise.
114  */
115 static inline bool
116 intel_wakeref_get_if_active(struct intel_wakeref *wf)
117 {
118 	return atomic_inc_not_zero(&wf->count);
119 }
120 
121 enum {
122 	INTEL_WAKEREF_PUT_ASYNC_BIT = 0,
123 	__INTEL_WAKEREF_PUT_LAST_BIT__
124 };
125 
126 static inline void
127 intel_wakeref_might_get(struct intel_wakeref *wf)
128 {
129 	might_lock(&wf->mutex);
130 }
131 
132 /**
133  * intel_wakeref_put_flags: Release the wakeref
134  * @wf: the wakeref
135  * @flags: control flags
136  *
137  * Release our hold on the wakeref. When there are no more users,
138  * the runtime pm wakeref will be released after the @fn callback is called
139  * underneath the wakeref mutex.
140  *
141  * Note that @fn is allowed to fail, in which case the runtime-pm wakeref
142  * is retained and an error reported.
143  *
144  * Returns: 0 if the wakeref was released successfully, or a negative error
145  * code otherwise.
146  */
147 static inline void
148 __intel_wakeref_put(struct intel_wakeref *wf, unsigned long flags)
149 #define INTEL_WAKEREF_PUT_ASYNC BIT(INTEL_WAKEREF_PUT_ASYNC_BIT)
150 #define INTEL_WAKEREF_PUT_DELAY \
151 	GENMASK(BITS_PER_LONG - 1, __INTEL_WAKEREF_PUT_LAST_BIT__)
152 {
153 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
154 	if (unlikely(!atomic_add_unless(&wf->count, -1, 1)))
155 		__intel_wakeref_put_last(wf, flags);
156 }
157 
158 static inline void
159 intel_wakeref_put(struct intel_wakeref *wf)
160 {
161 	might_sleep();
162 	__intel_wakeref_put(wf, 0);
163 }
164 
165 static inline void
166 intel_wakeref_put_async(struct intel_wakeref *wf)
167 {
168 	__intel_wakeref_put(wf, INTEL_WAKEREF_PUT_ASYNC);
169 }
170 
171 static inline void
172 intel_wakeref_put_delay(struct intel_wakeref *wf, unsigned long delay)
173 {
174 	__intel_wakeref_put(wf,
175 			    INTEL_WAKEREF_PUT_ASYNC |
176 			    FIELD_PREP(INTEL_WAKEREF_PUT_DELAY, delay));
177 }
178 
179 static inline void
180 intel_wakeref_might_put(struct intel_wakeref *wf)
181 {
182 	might_lock(&wf->mutex);
183 }
184 
185 /**
186  * intel_wakeref_lock: Lock the wakeref (mutex)
187  * @wf: the wakeref
188  *
189  * Locks the wakeref to prevent it being acquired or released. New users
190  * can still adjust the counter, but the wakeref itself (and callback)
191  * cannot be acquired or released.
192  */
193 static inline void
194 intel_wakeref_lock(struct intel_wakeref *wf)
195 	__acquires(wf->mutex)
196 {
197 	mutex_lock(&wf->mutex);
198 }
199 
200 /**
201  * intel_wakeref_unlock: Unlock the wakeref
202  * @wf: the wakeref
203  *
204  * Releases a previously acquired intel_wakeref_lock().
205  */
206 static inline void
207 intel_wakeref_unlock(struct intel_wakeref *wf)
208 	__releases(wf->mutex)
209 {
210 	mutex_unlock(&wf->mutex);
211 }
212 
213 /**
214  * intel_wakeref_unlock_wait: Wait until the active callback is complete
215  * @wf: the wakeref
216  *
217  * Waits for the active callback (under the @wf->mutex or another CPU) is
218  * complete.
219  */
220 static inline void
221 intel_wakeref_unlock_wait(struct intel_wakeref *wf)
222 {
223 	mutex_lock(&wf->mutex);
224 	mutex_unlock(&wf->mutex);
225 	flush_delayed_work(&wf->work);
226 }
227 
228 /**
229  * intel_wakeref_is_active: Query whether the wakeref is currently held
230  * @wf: the wakeref
231  *
232  * Returns: true if the wakeref is currently held.
233  */
234 static inline bool
235 intel_wakeref_is_active(const struct intel_wakeref *wf)
236 {
237 	return READ_ONCE(wf->wakeref);
238 }
239 
240 /**
241  * __intel_wakeref_defer_park: Defer the current park callback
242  * @wf: the wakeref
243  */
244 static inline void
245 __intel_wakeref_defer_park(struct intel_wakeref *wf)
246 {
247 	lockdep_assert_held(&wf->mutex);
248 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count));
249 	atomic_set_release(&wf->count, 1);
250 }
251 
252 /**
253  * intel_wakeref_wait_for_idle: Wait until the wakeref is idle
254  * @wf: the wakeref
255  *
256  * Wait for the earlier asynchronous release of the wakeref. Note
257  * this will wait for any third party as well, so make sure you only wait
258  * when you have control over the wakeref and trust no one else is acquiring
259  * it.
260  *
261  * Return: 0 on success, error code if killed.
262  */
263 int intel_wakeref_wait_for_idle(struct intel_wakeref *wf);
264 
265 struct intel_wakeref_auto {
266 	struct intel_runtime_pm *rpm;
267 	struct timer_list timer;
268 	intel_wakeref_t wakeref;
269 	spinlock_t lock;
270 	refcount_t count;
271 };
272 
273 /**
274  * intel_wakeref_auto: Delay the runtime-pm autosuspend
275  * @wf: the wakeref
276  * @timeout: relative timeout in jiffies
277  *
278  * The runtime-pm core uses a suspend delay after the last wakeref
279  * is released before triggering runtime suspend of the device. That
280  * delay is configurable via sysfs with little regard to the device
281  * characteristics. Instead, we want to tune the autosuspend based on our
282  * HW knowledge. intel_wakeref_auto() delays the sleep by the supplied
283  * timeout.
284  *
285  * Pass @timeout = 0 to cancel a previous autosuspend by executing the
286  * suspend immediately.
287  */
288 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout);
289 
290 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
291 			     struct intel_runtime_pm *rpm);
292 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf);
293 
294 #endif /* INTEL_WAKEREF_H */
295