| /* |
| * Copyright (C) 2012 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef ANDROID_DISPSYNC_H |
| #define ANDROID_DISPSYNC_H |
| |
| #include <stddef.h> |
| |
| #include <utils/Mutex.h> |
| #include <utils/Timers.h> |
| #include <utils/RefBase.h> |
| |
| namespace android { |
| |
| // Ignore present (retire) fences if the device doesn't have support for the |
| // sync framework, or if all phase offsets are zero. The latter is useful |
| // because it allows us to avoid resync bursts on devices that don't need |
| // phase-offset VSYNC events. |
| #if defined(RUNNING_WITHOUT_SYNC_FRAMEWORK) || \ |
| (VSYNC_EVENT_PHASE_OFFSET_NS == 0 && SF_VSYNC_EVENT_PHASE_OFFSET_NS == 0) |
| static const bool kIgnorePresentFences = true; |
| #else |
| static const bool kIgnorePresentFences = false; |
| #endif |
| |
| |
| class String8; |
| class Fence; |
| class DispSyncThread; |
| |
| // DispSync maintains a model of the periodic hardware-based vsync events of a |
| // display and uses that model to execute period callbacks at specific phase |
| // offsets from the hardware vsync events. The model is constructed by |
| // feeding consecutive hardware event timestamps to the DispSync object via |
| // the addResyncSample method. |
| // |
| // The model is validated using timestamps from Fence objects that are passed |
| // to the DispSync object via the addPresentFence method. These fence |
| // timestamps should correspond to a hardware vsync event, but they need not |
| // be consecutive hardware vsync times. If this method determines that the |
| // current model accurately represents the hardware event times it will return |
| // false to indicate that a resynchronization (via addResyncSample) is not |
| // needed. |
| class DispSync { |
| |
| public: |
| |
| class Callback: public virtual RefBase { |
| public: |
| virtual ~Callback() {}; |
| virtual void onDispSyncEvent(nsecs_t when) = 0; |
| }; |
| |
| DispSync(); |
| ~DispSync(); |
| |
| // reset clears the resync samples and error value. |
| void reset(); |
| |
| // addPresentFence adds a fence for use in validating the current vsync |
| // event model. The fence need not be signaled at the time |
| // addPresentFence is called. When the fence does signal, its timestamp |
| // should correspond to a hardware vsync event. Unlike the |
| // addResyncSample method, the timestamps of consecutive fences need not |
| // correspond to consecutive hardware vsync events. |
| // |
| // This method should be called with the retire fence from each HWComposer |
| // set call that affects the display. |
| bool addPresentFence(const sp<Fence>& fence); |
| |
| // The beginResync, addResyncSample, and endResync methods are used to re- |
| // synchronize the DispSync's model to the hardware vsync events. The re- |
| // synchronization process involves first calling beginResync, then |
| // calling addResyncSample with a sequence of consecutive hardware vsync |
| // event timestamps, and finally calling endResync when addResyncSample |
| // indicates that no more samples are needed by returning false. |
| // |
| // This resynchronization process should be performed whenever the display |
| // is turned on (i.e. once immediately after it's turned on) and whenever |
| // addPresentFence returns true indicating that the model has drifted away |
| // from the hardware vsync events. |
| void beginResync(); |
| bool addResyncSample(nsecs_t timestamp); |
| void endResync(); |
| |
| // The setPeriod method sets the vsync event model's period to a specific |
| // value. This should be used to prime the model when a display is first |
| // turned on. It should NOT be used after that. |
| void setPeriod(nsecs_t period); |
| |
| // setRefreshSkipCount specifies an additional number of refresh |
| // cycles to skip. For example, on a 60Hz display, a skip count of 1 |
| // will result in events happening at 30Hz. Default is zero. The idea |
| // is to sacrifice smoothness for battery life. |
| void setRefreshSkipCount(int count); |
| |
| // addEventListener registers a callback to be called repeatedly at the |
| // given phase offset from the hardware vsync events. The callback is |
| // called from a separate thread and it should return reasonably quickly |
| // (i.e. within a few hundred microseconds). |
| status_t addEventListener(nsecs_t phase, const sp<Callback>& callback); |
| |
| // removeEventListener removes an already-registered event callback. Once |
| // this method returns that callback will no longer be called by the |
| // DispSync object. |
| status_t removeEventListener(const sp<Callback>& callback); |
| |
| // computeNextRefresh computes when the next refresh is expected to begin. |
| // The periodOffset value can be used to move forward or backward; an |
| // offset of zero is the next refresh, -1 is the previous refresh, 1 is |
| // the refresh after next. etc. |
| nsecs_t computeNextRefresh(int periodOffset) const; |
| |
| // dump appends human-readable debug info to the result string. |
| void dump(String8& result) const; |
| |
| private: |
| |
| void updateModelLocked(); |
| void updateErrorLocked(); |
| void resetErrorLocked(); |
| |
| enum { MAX_RESYNC_SAMPLES = 32 }; |
| enum { MIN_RESYNC_SAMPLES_FOR_UPDATE = 3 }; |
| enum { NUM_PRESENT_SAMPLES = 8 }; |
| enum { MAX_RESYNC_SAMPLES_WITHOUT_PRESENT = 12 }; |
| |
| // mPeriod is the computed period of the modeled vsync events in |
| // nanoseconds. |
| nsecs_t mPeriod; |
| |
| // mPhase is the phase offset of the modeled vsync events. It is the |
| // number of nanoseconds from time 0 to the first vsync event. |
| nsecs_t mPhase; |
| |
| // mError is the computed model error. It is based on the difference |
| // between the estimated vsync event times and those observed in the |
| // mPresentTimes array. |
| nsecs_t mError; |
| |
| // These member variables are the state used during the resynchronization |
| // process to store information about the hardware vsync event times used |
| // to compute the model. |
| nsecs_t mResyncSamples[MAX_RESYNC_SAMPLES]; |
| size_t mFirstResyncSample; |
| size_t mNumResyncSamples; |
| int mNumResyncSamplesSincePresent; |
| |
| // These member variables store information about the present fences used |
| // to validate the currently computed model. |
| sp<Fence> mPresentFences[NUM_PRESENT_SAMPLES]; |
| nsecs_t mPresentTimes[NUM_PRESENT_SAMPLES]; |
| size_t mPresentSampleOffset; |
| |
| int mRefreshSkipCount; |
| |
| // mThread is the thread from which all the callbacks are called. |
| sp<DispSyncThread> mThread; |
| |
| // mMutex is used to protect access to all member variables. |
| mutable Mutex mMutex; |
| }; |
| |
| } |
| |
| #endif // ANDROID_DISPSYNC_H |