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 	if (!atomic_dec_and_test(&wf->count))
58 		goto unlock;
59 
60 	/* ops->put() must reschedule its own release on error/deferral */
61 	if (likely(!wf->ops->put(wf))) {
62 		rpm_put(wf);
63 		wake_up_var(&wf->wakeref);
64 	}
65 
66 unlock:
67 	mutex_unlock(&wf->mutex);
68 }
69 
70 void __intel_wakeref_put_last(struct intel_wakeref *wf)
71 {
72 	INTEL_WAKEREF_BUG_ON(work_pending(&wf->work));
73 
74 	/* Assume we are not in process context and so cannot sleep. */
75 	if (wf->ops->flags & INTEL_WAKEREF_PUT_ASYNC ||
76 	    !mutex_trylock(&wf->mutex)) {
77 		schedule_work(&wf->work);
78 		return;
79 	}
80 
81 	____intel_wakeref_put_last(wf);
82 }
83 
84 static void __intel_wakeref_put_work(struct work_struct *wrk)
85 {
86 	struct intel_wakeref *wf = container_of(wrk, typeof(*wf), work);
87 
88 	if (atomic_add_unless(&wf->count, -1, 1))
89 		return;
90 
91 	mutex_lock(&wf->mutex);
92 	____intel_wakeref_put_last(wf);
93 }
94 
95 void __intel_wakeref_init(struct intel_wakeref *wf,
96 			  struct intel_runtime_pm *rpm,
97 			  const struct intel_wakeref_ops *ops,
98 			  struct lock_class_key *key)
99 {
100 	wf->rpm = rpm;
101 	wf->ops = ops;
102 
103 	__mutex_init(&wf->mutex, "wakeref", key);
104 	atomic_set(&wf->count, 0);
105 	wf->wakeref = 0;
106 
107 	INIT_WORK(&wf->work, __intel_wakeref_put_work);
108 }
109 
110 int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
111 {
112 	return wait_var_event_killable(&wf->wakeref,
113 				       !intel_wakeref_is_active(wf));
114 }
115 
116 static void wakeref_auto_timeout(struct timer_list *t)
117 {
118 	struct intel_wakeref_auto *wf = from_timer(wf, t, timer);
119 	intel_wakeref_t wakeref;
120 	unsigned long flags;
121 
122 	if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
123 		return;
124 
125 	wakeref = fetch_and_zero(&wf->wakeref);
126 	spin_unlock_irqrestore(&wf->lock, flags);
127 
128 	intel_runtime_pm_put(wf->rpm, wakeref);
129 }
130 
131 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
132 			     struct intel_runtime_pm *rpm)
133 {
134 	spin_lock_init(&wf->lock);
135 	timer_setup(&wf->timer, wakeref_auto_timeout, 0);
136 	refcount_set(&wf->count, 0);
137 	wf->wakeref = 0;
138 	wf->rpm = rpm;
139 }
140 
141 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
142 {
143 	unsigned long flags;
144 
145 	if (!timeout) {
146 		if (del_timer_sync(&wf->timer))
147 			wakeref_auto_timeout(&wf->timer);
148 		return;
149 	}
150 
151 	/* Our mission is that we only extend an already active wakeref */
152 	assert_rpm_wakelock_held(wf->rpm);
153 
154 	if (!refcount_inc_not_zero(&wf->count)) {
155 		spin_lock_irqsave(&wf->lock, flags);
156 		if (!refcount_inc_not_zero(&wf->count)) {
157 			INTEL_WAKEREF_BUG_ON(wf->wakeref);
158 			wf->wakeref = intel_runtime_pm_get_if_in_use(wf->rpm);
159 			refcount_set(&wf->count, 1);
160 		}
161 		spin_unlock_irqrestore(&wf->lock, flags);
162 	}
163 
164 	/*
165 	 * If we extend a pending timer, we will only get a single timer
166 	 * callback and so need to cancel the local inc by running the
167 	 * elided callback to keep the wf->count balanced.
168 	 */
169 	if (mod_timer(&wf->timer, jiffies + timeout))
170 		wakeref_auto_timeout(&wf->timer);
171 }
172 
173 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf)
174 {
175 	intel_wakeref_auto(wf, 0);
176 	INTEL_WAKEREF_BUG_ON(wf->wakeref);
177 }
178