1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6 
7 #include <linux/wait_bit.h>
8 
9 #include "intel_runtime_pm.h"
10 #include "intel_wakeref.h"
11 
12 static void rpm_get(struct intel_wakeref *wf)
13 {
14 	wf->wakeref = intel_runtime_pm_get(wf->rpm);
15 }
16 
17 static void rpm_put(struct intel_wakeref *wf)
18 {
19 	intel_wakeref_t wakeref = fetch_and_zero(&wf->wakeref);
20 
21 	intel_runtime_pm_put(wf->rpm, wakeref);
22 	INTEL_WAKEREF_BUG_ON(!wakeref);
23 }
24 
25 int __intel_wakeref_get_first(struct intel_wakeref *wf)
26 {
27 	/*
28 	 * Treat get/put as different subclasses, as we may need to run
29 	 * the put callback from under the shrinker and do not want to
30 	 * cross-contanimate that callback with any extra work performed
31 	 * upon acquiring the wakeref.
32 	 */
33 	mutex_lock_nested(&wf->mutex, SINGLE_DEPTH_NESTING);
34 	if (!atomic_read(&wf->count)) {
35 		int err;
36 
37 		rpm_get(wf);
38 
39 		err = wf->ops->get(wf);
40 		if (unlikely(err)) {
41 			rpm_put(wf);
42 			mutex_unlock(&wf->mutex);
43 			return err;
44 		}
45 
46 		smp_mb__before_atomic(); /* release wf->count */
47 	}
48 	atomic_inc(&wf->count);
49 	mutex_unlock(&wf->mutex);
50 
51 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
52 	return 0;
53 }
54 
55 static void ____intel_wakeref_put_last(struct intel_wakeref *wf)
56 {
57 	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
58 	if (unlikely(!atomic_dec_and_test(&wf->count)))
59 		goto unlock;
60 
61 	/* ops->put() must reschedule its own release on error/deferral */
62 	if (likely(!wf->ops->put(wf))) {
63 		rpm_put(wf);
64 		wake_up_var(&wf->wakeref);
65 	}
66 
67 unlock:
68 	mutex_unlock(&wf->mutex);
69 }
70 
71 void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags)
72 {
73 	INTEL_WAKEREF_BUG_ON(delayed_work_pending(&wf->work));
74 
75 	/* Assume we are not in process context and so cannot sleep. */
76 	if (flags & INTEL_WAKEREF_PUT_ASYNC || !mutex_trylock(&wf->mutex)) {
77 		mod_delayed_work(system_wq, &wf->work,
78 				 FIELD_GET(INTEL_WAKEREF_PUT_DELAY, flags));
79 		return;
80 	}
81 
82 	____intel_wakeref_put_last(wf);
83 }
84 
85 static void __intel_wakeref_put_work(struct work_struct *wrk)
86 {
87 	struct intel_wakeref *wf = container_of(wrk, typeof(*wf), work.work);
88 
89 	if (atomic_add_unless(&wf->count, -1, 1))
90 		return;
91 
92 	mutex_lock(&wf->mutex);
93 	____intel_wakeref_put_last(wf);
94 }
95 
96 void __intel_wakeref_init(struct intel_wakeref *wf,
97 			  struct intel_runtime_pm *rpm,
98 			  const struct intel_wakeref_ops *ops,
99 			  struct intel_wakeref_lockclass *key)
100 {
101 	wf->rpm = rpm;
102 	wf->ops = ops;
103 
104 	__mutex_init(&wf->mutex, "wakeref.mutex", &key->mutex);
105 	atomic_set(&wf->count, 0);
106 	wf->wakeref = 0;
107 
108 	INIT_DELAYED_WORK(&wf->work, __intel_wakeref_put_work);
109 	lockdep_init_map(&wf->work.work.lockdep_map,
110 			 "wakeref.work", &key->work, 0);
111 }
112 
113 int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
114 {
115 	int err;
116 
117 	might_sleep();
118 
119 	err = wait_var_event_killable(&wf->wakeref,
120 				      !intel_wakeref_is_active(wf));
121 	if (err)
122 		return err;
123 
124 	intel_wakeref_unlock_wait(wf);
125 	return 0;
126 }
127 
128 static void wakeref_auto_timeout(struct timer_list *t)
129 {
130 	struct intel_wakeref_auto *wf = from_timer(wf, t, timer);
131 	intel_wakeref_t wakeref;
132 	unsigned long flags;
133 
134 	if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
135 		return;
136 
137 	wakeref = fetch_and_zero(&wf->wakeref);
138 	spin_unlock_irqrestore(&wf->lock, flags);
139 
140 	intel_runtime_pm_put(wf->rpm, wakeref);
141 }
142 
143 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
144 			     struct intel_runtime_pm *rpm)
145 {
146 	spin_lock_init(&wf->lock);
147 	timer_setup(&wf->timer, wakeref_auto_timeout, 0);
148 	refcount_set(&wf->count, 0);
149 	wf->wakeref = 0;
150 	wf->rpm = rpm;
151 }
152 
153 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
154 {
155 	unsigned long flags;
156 
157 	if (!timeout) {
158 		if (del_timer_sync(&wf->timer))
159 			wakeref_auto_timeout(&wf->timer);
160 		return;
161 	}
162 
163 	/* Our mission is that we only extend an already active wakeref */
164 	assert_rpm_wakelock_held(wf->rpm);
165 
166 	if (!refcount_inc_not_zero(&wf->count)) {
167 		spin_lock_irqsave(&wf->lock, flags);
168 		if (!refcount_inc_not_zero(&wf->count)) {
169 			INTEL_WAKEREF_BUG_ON(wf->wakeref);
170 			wf->wakeref = intel_runtime_pm_get_if_in_use(wf->rpm);
171 			refcount_set(&wf->count, 1);
172 		}
173 		spin_unlock_irqrestore(&wf->lock, flags);
174 	}
175 
176 	/*
177 	 * If we extend a pending timer, we will only get a single timer
178 	 * callback and so need to cancel the local inc by running the
179 	 * elided callback to keep the wf->count balanced.
180 	 */
181 	if (mod_timer(&wf->timer, jiffies + timeout))
182 		wakeref_auto_timeout(&wf->timer);
183 }
184 
185 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf)
186 {
187 	intel_wakeref_auto(wf, 0);
188 	INTEL_WAKEREF_BUG_ON(wf->wakeref);
189 }
190