41d67d7ab4
Get the next refresh time from DispSync instead of guessing based on the current time. Change-Id: I8dc72a3217bfd4e9b4c905034194d1a298cad69a
159 lines
6.0 KiB
C++
159 lines
6.0 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_DISPSYNC_H
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#define ANDROID_DISPSYNC_H
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#include <stddef.h>
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#include <utils/Mutex.h>
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#include <utils/Timers.h>
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#include <utils/RefBase.h>
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namespace android {
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class String8;
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class Fence;
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class DispSyncThread;
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// DispSync maintains a model of the periodic hardware-based vsync events of a
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// display and uses that model to execute period callbacks at specific phase
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// offsets from the hardware vsync events. The model is constructed by
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// feeding consecutive hardware event timestamps to the DispSync object via
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// the addResyncSample method.
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//
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// The model is validated using timestamps from Fence objects that are passed
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// to the DispSync object via the addPresentFence method. These fence
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// timestamps should correspond to a hardware vsync event, but they need not
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// be consecutive hardware vsync times. If this method determines that the
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// current model accurately represents the hardware event times it will return
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// false to indicate that a resynchronization (via addResyncSample) is not
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// needed.
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class DispSync {
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public:
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class Callback: public virtual RefBase {
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public:
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virtual ~Callback() {};
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virtual void onDispSyncEvent(nsecs_t when) = 0;
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};
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DispSync();
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~DispSync();
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void reset();
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// addPresentFence adds a fence for use in validating the current vsync
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// event model. The fence need not be signaled at the time
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// addPresentFence is called. When the fence does signal, its timestamp
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// should correspond to a hardware vsync event. Unlike the
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// addResyncSample method, the timestamps of consecutive fences need not
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// correspond to consecutive hardware vsync events.
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//
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// This method should be called with the retire fence from each HWComposer
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// set call that affects the display.
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bool addPresentFence(const sp<Fence>& fence);
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// The beginResync, addResyncSample, and endResync methods are used to re-
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// synchronize the DispSync's model to the hardware vsync events. The re-
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// synchronization process involves first calling beginResync, then
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// calling addResyncSample with a sequence of consecutive hardware vsync
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// event timestamps, and finally calling endResync when addResyncSample
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// indicates that no more samples are needed by returning false.
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//
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// This resynchronization process should be performed whenever the display
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// is turned on (i.e. once immediately after it's turned on) and whenever
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// addPresentFence returns true indicating that the model has drifted away
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// from the hardware vsync events.
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void beginResync();
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bool addResyncSample(nsecs_t timestamp);
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void endResync();
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// The setPeriod method sets the vsync event model's period to a specific
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// value. This should be used to prime the model when a display is first
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// turned on. It should NOT be used after that.
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void setPeriod(nsecs_t period);
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// Setting the low power mode reduces the frame rate to half of the default
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void setLowPowerMode(bool enabled);
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// addEventListener registers a callback to be called repeatedly at the
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// given phase offset from the hardware vsync events. The callback is
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// called from a separate thread and it should return reasonably quickly
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// (i.e. within a few hundred microseconds).
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status_t addEventListener(nsecs_t phase, const sp<Callback>& callback);
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// removeEventListener removes an already-registered event callback. Once
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// this method returns that callback will no longer be called by the
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// DispSync object.
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status_t removeEventListener(const sp<Callback>& callback);
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// computeNextRefresh computes when the next refresh is expected to begin.
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// The periodOffset value can be used to move forward or backward; an
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// offset of zero is the next refresh, -1 is the previous refresh, 1 is
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// the refresh after next. etc.
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nsecs_t computeNextRefresh(int periodOffset) const;
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private:
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void updateModelLocked();
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void updateErrorLocked();
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void resetErrorLocked();
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enum { MAX_RESYNC_SAMPLES = 32 };
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enum { MIN_RESYNC_SAMPLES_FOR_UPDATE = 3 };
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enum { NUM_PRESENT_SAMPLES = 8 };
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enum { MAX_RESYNC_SAMPLES_WITHOUT_PRESENT = 12 };
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// mPeriod is the computed period of the modeled vsync events in
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// nanoseconds.
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nsecs_t mPeriod;
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// mPhase is the phase offset of the modeled vsync events. It is the
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// number of nanoseconds from time 0 to the first vsync event.
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nsecs_t mPhase;
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// mError is the computed model error. It is based on the difference
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// between the estimated vsync event times and those observed in the
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// mPresentTimes array.
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nsecs_t mError;
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// These member variables are the state used during the resynchronization
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// process to store information about the hardware vsync event times used
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// to compute the model.
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nsecs_t mResyncSamples[MAX_RESYNC_SAMPLES];
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size_t mFirstResyncSample;
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size_t mNumResyncSamples;
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int mNumResyncSamplesSincePresent;
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// These member variables store information about the present fences used
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// to validate the currently computed model.
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sp<Fence> mPresentFences[NUM_PRESENT_SAMPLES];
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nsecs_t mPresentTimes[NUM_PRESENT_SAMPLES];
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size_t mPresentSampleOffset;
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// mThread is the thread from which all the callbacks are called.
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sp<DispSyncThread> mThread;
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// mMutex is used to protect access to all member variables.
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mutable Mutex mMutex;
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};
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}
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#endif // ANDROID_DISPSYNC_H
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