1 /*
2  * Copyright 2019 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <utils/Timers.h>
20 #include "Fps.h"
21 #include "VSyncDispatch.h"
22 
23 namespace android::scheduler {
24 /*
25  * VSyncTracker is an interface for providing estimates on future Vsync signal times based on
26  * historical vsync timing data.
27  */
28 class VSyncTracker {
29 public:
30     virtual ~VSyncTracker();
31 
32     /*
33      * Adds a known timestamp from a vsync timing source (HWVsync signal, present fence)
34      * to the model.
35      *
36      * \param [in] timestamp    The timestamp when the vsync signal was.
37      * \return                  True if the timestamp was consistent with the internal model,
38      *                          False otherwise
39      */
40     virtual bool addVsyncTimestamp(nsecs_t timestamp) = 0;
41 
42     /*
43      * Access the next anticipated vsync time such that the anticipated time >= timePoint.
44      * This will always give the best accurate at the time of calling; multiple
45      * calls with the same timePoint might give differing values if the internal model
46      * is updated.
47      *
48      * \param [in] timePoint    The point in time after which to estimate a vsync event.
49      * \return                  A prediction of the timestamp of a vsync event.
50      */
51     virtual nsecs_t nextAnticipatedVSyncTimeFrom(nsecs_t timePoint) const = 0;
52 
53     /*
54      * The current period of the vsync signal.
55      *
56      * \return  The current period of the vsync signal
57      */
58     virtual nsecs_t currentPeriod() const = 0;
59 
60     /*
61      * Inform the tracker that the period is changing and the tracker needs to recalibrate itself.
62      *
63      * \param [in] period   The period that the system is changing into.
64      */
65     virtual void setPeriod(nsecs_t period) = 0;
66 
67     /* Inform the tracker that the samples it has are not accurate for prediction. */
68     virtual void resetModel() = 0;
69 
70     virtual bool needsMoreSamples() const = 0;
71 
72     /*
73      * Checks if a vsync timestamp is in phase for a frame rate
74      *
75      * \param [in] timePoint  A vsync timestamp
76      * \param [in] frameRate  The frame rate to check for
77      */
78     virtual bool isVSyncInPhase(nsecs_t timePoint, Fps frameRate) const = 0;
79 
80     virtual void dump(std::string& result) const = 0;
81 
82 protected:
83     VSyncTracker(VSyncTracker const&) = delete;
84     VSyncTracker& operator=(VSyncTracker const&) = delete;
85     VSyncTracker() = default;
86 };
87 
88 } // namespace android::scheduler
89