1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6 
7 #include "intel_drv.h"
8 #include "intel_wakeref.h"
9 
10 static void rpm_get(struct drm_i915_private *i915, struct intel_wakeref *wf)
11 {
12 	wf->wakeref = intel_runtime_pm_get(i915);
13 }
14 
15 static void rpm_put(struct drm_i915_private *i915, struct intel_wakeref *wf)
16 {
17 	intel_wakeref_t wakeref = fetch_and_zero(&wf->wakeref);
18 
19 	intel_runtime_pm_put(i915, wakeref);
20 	GEM_BUG_ON(!wakeref);
21 }
22 
23 int __intel_wakeref_get_first(struct drm_i915_private *i915,
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(i915, wf);
38 
39 		err = fn(wf);
40 		if (unlikely(err)) {
41 			rpm_put(i915, 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 drm_i915_private *i915,
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(i915, 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