1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6 
7 #include "intel_runtime_pm.h"
8 #include "i915_gem.h"
9 
10 static void rpm_get(struct intel_runtime_pm *rpm, struct intel_wakeref *wf)
11 {
12 	wf->wakeref = intel_runtime_pm_get(rpm);
13 }
14 
15 static void rpm_put(struct intel_runtime_pm *rpm, struct intel_wakeref *wf)
16 {
17 	intel_wakeref_t wakeref = fetch_and_zero(&wf->wakeref);
18 
19 	intel_runtime_pm_put(rpm, wakeref);
20 	GEM_BUG_ON(!wakeref);
21 }
22 
23 int __intel_wakeref_get_first(struct intel_runtime_pm *rpm,
24 			      struct intel_wakeref *wf,
25 			      int (*fn)(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(rpm, wf);
38 
39 		err = fn(wf);
40 		if (unlikely(err)) {
41 			rpm_put(rpm, 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 	return 0;
52 }
53 
54 int __intel_wakeref_put_last(struct intel_runtime_pm *rpm,
55 			     struct intel_wakeref *wf,
56 			     int (*fn)(struct intel_wakeref *wf))
57 {
58 	int err;
59 
60 	err = fn(wf);
61 	if (likely(!err))
62 		rpm_put(rpm, wf);
63 	else
64 		atomic_inc(&wf->count);
65 	mutex_unlock(&wf->mutex);
66 
67 	return err;
68 }
69 
70 void __intel_wakeref_init(struct intel_wakeref *wf, struct lock_class_key *key)
71 {
72 	__mutex_init(&wf->mutex, "wakeref", key);
73 	atomic_set(&wf->count, 0);
74 	wf->wakeref = 0;
75 }
76 
77 static void wakeref_auto_timeout(struct timer_list *t)
78 {
79 	struct intel_wakeref_auto *wf = from_timer(wf, t, timer);
80 	intel_wakeref_t wakeref;
81 	unsigned long flags;
82 
83 	if (!refcount_dec_and_lock_irqsave(&wf->count, &wf->lock, &flags))
84 		return;
85 
86 	wakeref = fetch_and_zero(&wf->wakeref);
87 	spin_unlock_irqrestore(&wf->lock, flags);
88 
89 	intel_runtime_pm_put(wf->rpm, wakeref);
90 }
91 
92 void intel_wakeref_auto_init(struct intel_wakeref_auto *wf,
93 			     struct intel_runtime_pm *rpm)
94 {
95 	spin_lock_init(&wf->lock);
96 	timer_setup(&wf->timer, wakeref_auto_timeout, 0);
97 	refcount_set(&wf->count, 0);
98 	wf->wakeref = 0;
99 	wf->rpm = rpm;
100 }
101 
102 void intel_wakeref_auto(struct intel_wakeref_auto *wf, unsigned long timeout)
103 {
104 	unsigned long flags;
105 
106 	if (!timeout) {
107 		if (del_timer_sync(&wf->timer))
108 			wakeref_auto_timeout(&wf->timer);
109 		return;
110 	}
111 
112 	/* Our mission is that we only extend an already active wakeref */
113 	assert_rpm_wakelock_held(wf->rpm);
114 
115 	if (!refcount_inc_not_zero(&wf->count)) {
116 		spin_lock_irqsave(&wf->lock, flags);
117 		if (!refcount_inc_not_zero(&wf->count)) {
118 			GEM_BUG_ON(wf->wakeref);
119 			wf->wakeref = intel_runtime_pm_get_if_in_use(wf->rpm);
120 			refcount_set(&wf->count, 1);
121 		}
122 		spin_unlock_irqrestore(&wf->lock, flags);
123 	}
124 
125 	/*
126 	 * If we extend a pending timer, we will only get a single timer
127 	 * callback and so need to cancel the local inc by running the
128 	 * elided callback to keep the wf->count balanced.
129 	 */
130 	if (mod_timer(&wf->timer, jiffies + timeout))
131 		wakeref_auto_timeout(&wf->timer);
132 }
133 
134 void intel_wakeref_auto_fini(struct intel_wakeref_auto *wf)
135 {
136 	intel_wakeref_auto(wf, 0);
137 	GEM_BUG_ON(wf->wakeref);
138 }
139