EventThread.cpp revision 22ffb117b0c2a906bd04aef9738a52223cdd1dce 
1/*
2 * Copyright (C) 2011 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#define ATRACE_TAG ATRACE_TAG_GRAPHICS
18
19#include <stdint.h>
20#include <sys/types.h>
21
22#include <gui/BitTube.h>
23#include <gui/IDisplayEventConnection.h>
24#include <gui/DisplayEventReceiver.h>
25
26#include <utils/Errors.h>
27#include <utils/Trace.h>
28
29#include "DisplayHardware/DisplayHardware.h"
30#include "EventThread.h"
31#include "SurfaceFlinger.h"
32
33// ---------------------------------------------------------------------------
34
35namespace android {
36
37// ---------------------------------------------------------------------------
38
39EventThread::EventThread(const sp<SurfaceFlinger>& flinger)
40    : mFlinger(flinger),
41      mHw(flinger->graphicPlane(0).editDisplayHardware()),
42      mLastVSyncTimestamp(0),
43      mVSyncTimestamp(0),
44      mUseSoftwareVSync(false),
45      mDeliveredEvents(0),
46      mDebugVsyncEnabled(false)
47{
48}
49
50void EventThread::onFirstRef() {
51    mHw.setVSyncHandler(this);
52    run("EventThread", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
53}
54
55sp<EventThread::Connection> EventThread::createEventConnection() const {
56    return new Connection(const_cast<EventThread*>(this));
57}
58
59status_t EventThread::registerDisplayEventConnection(
60        const sp<EventThread::Connection>& connection) {
61    Mutex::Autolock _l(mLock);
62    mDisplayEventConnections.add(connection);
63    mCondition.signal();
64    return NO_ERROR;
65}
66
67status_t EventThread::unregisterDisplayEventConnection(
68        const wp<EventThread::Connection>& connection) {
69    Mutex::Autolock _l(mLock);
70    mDisplayEventConnections.remove(connection);
71    mCondition.signal();
72    return NO_ERROR;
73}
74
75void EventThread::removeDisplayEventConnection(
76        const wp<EventThread::Connection>& connection) {
77    Mutex::Autolock _l(mLock);
78    mDisplayEventConnections.remove(connection);
79}
80
81void EventThread::setVsyncRate(uint32_t count,
82        const sp<EventThread::Connection>& connection) {
83    if (int32_t(count) >= 0) { // server must protect against bad params
84        Mutex::Autolock _l(mLock);
85        const int32_t new_count = (count == 0) ? -1 : count;
86        if (connection->count != new_count) {
87            connection->count = new_count;
88            mCondition.signal();
89        }
90    }
91}
92
93void EventThread::requestNextVsync(
94        const sp<EventThread::Connection>& connection) {
95    Mutex::Autolock _l(mLock);
96    if (connection->count < 0) {
97        connection->count = 0;
98        mCondition.signal();
99    }
100}
101
102void EventThread::onScreenReleased() {
103    Mutex::Autolock _l(mLock);
104    // wait for an eventual pending vsync to be serviced
105    if (!mUseSoftwareVSync) {
106        while (mVSyncTimestamp) {
107            mCondition.wait(mLock);
108        }
109    }
110    // disable reliance on h/w vsync
111    mUseSoftwareVSync = true;
112}
113
114void EventThread::onScreenAcquired() {
115    Mutex::Autolock _l(mLock);
116    mUseSoftwareVSync = false;
117}
118
119
120void EventThread::onVSyncReceived(int, nsecs_t timestamp) {
121    Mutex::Autolock _l(mLock);
122    mVSyncTimestamp = timestamp;
123    mCondition.signal();
124}
125
126bool EventThread::threadLoop() {
127
128    nsecs_t timestamp;
129    DisplayEventReceiver::Event vsync;
130    Vector< wp<EventThread::Connection> > displayEventConnections;
131
132    do {
133        Mutex::Autolock _l(mLock);
134        do {
135            // latch VSYNC event if any
136            timestamp = mVSyncTimestamp;
137            mVSyncTimestamp = 0;
138
139            // check if we should be waiting for VSYNC events
140            bool waitForNextVsync = false;
141            size_t count = mDisplayEventConnections.size();
142            for (size_t i=0 ; i<count ; i++) {
143                sp<Connection> connection =
144                        mDisplayEventConnections.itemAt(i).promote();
145                if (connection!=0 && connection->count >= 0) {
146                    // at least one continuous mode or active one-shot event
147                    waitForNextVsync = true;
148                    break;
149                }
150            }
151
152            if (timestamp) {
153                if (!waitForNextVsync) {
154                    // we received a VSYNC but we have no clients
155                    // don't report it, and disable VSYNC events
156                    disableVSyncLocked();
157                } else {
158                    // report VSYNC event
159                    break;
160                }
161            } else {
162                // never disable VSYNC events immediately, instead
163                // we'll wait to receive the event and we'll
164                // reevaluate whether we need to dispatch it and/or
165                // disable VSYNC events then.
166                if (waitForNextVsync) {
167                    // enable
168                    enableVSyncLocked();
169                }
170            }
171
172            // wait for something to happen
173            if (mUseSoftwareVSync == true) {
174                // h/w vsync cannot be used (screen is off), so we use
175                // a  timeout instead. it doesn't matter how imprecise this
176                // is, we just need to make sure to serve the clients
177                if (mCondition.waitRelative(mLock, ms2ns(16)) == TIMED_OUT) {
178                    mVSyncTimestamp = systemTime(SYSTEM_TIME_MONOTONIC);
179                }
180            } else {
181                mCondition.wait(mLock);
182            }
183        } while(true);
184
185        // process vsync event
186        mDeliveredEvents++;
187        mLastVSyncTimestamp = timestamp;
188
189        // now see if we still need to report this VSYNC event
190        const size_t count = mDisplayEventConnections.size();
191        for (size_t i=0 ; i<count ; i++) {
192            bool reportVsync = false;
193            sp<Connection> connection =
194                    mDisplayEventConnections.itemAt(i).promote();
195            if (connection == 0)
196                continue;
197
198            const int32_t count = connection->count;
199            if (count >= 1) {
200                if (count==1 || (mDeliveredEvents % count) == 0) {
201                    // continuous event, and time to report it
202                    reportVsync = true;
203                }
204            } else if (count >= -1) {
205                if (count == 0) {
206                    // fired this time around
207                    reportVsync = true;
208                }
209                connection->count--;
210            }
211            if (reportVsync) {
212                displayEventConnections.add(connection);
213            }
214        }
215    } while (!displayEventConnections.size());
216
217    // dispatch vsync events to listeners...
218    vsync.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
219    vsync.header.timestamp = timestamp;
220    vsync.vsync.count = mDeliveredEvents;
221
222    const size_t count = displayEventConnections.size();
223    for (size_t i=0 ; i<count ; i++) {
224        sp<Connection> conn(displayEventConnections[i].promote());
225        // make sure the connection didn't die
226        if (conn != NULL) {
227            status_t err = conn->postEvent(vsync);
228            if (err == -EAGAIN || err == -EWOULDBLOCK) {
229                // The destination doesn't accept events anymore, it's probably
230                // full. For now, we just drop the events on the floor.
231                // Note that some events cannot be dropped and would have to be
232                // re-sent later. Right-now we don't have the ability to do
233                // this, but it doesn't matter for VSYNC.
234            } else if (err < 0) {
235                // handle any other error on the pipe as fatal. the only
236                // reasonable thing to do is to clean-up this connection.
237                // The most common error we'll get here is -EPIPE.
238                removeDisplayEventConnection(displayEventConnections[i]);
239            }
240        } else {
241            // somehow the connection is dead, but we still have it in our list
242            // just clean the list.
243            removeDisplayEventConnection(displayEventConnections[i]);
244        }
245    }
246
247    // clear all our references without holding mLock
248    displayEventConnections.clear();
249
250    return true;
251}
252
253void EventThread::enableVSyncLocked() {
254    if (!mUseSoftwareVSync) {
255        // never enable h/w VSYNC when screen is off
256        mHw.getHwComposer().eventControl(HWComposer::EVENT_VSYNC, true);
257    }
258    mDebugVsyncEnabled = true;
259}
260
261void EventThread::disableVSyncLocked() {
262    mHw.getHwComposer().eventControl(HWComposer::EVENT_VSYNC, false);
263    mDebugVsyncEnabled = false;
264}
265
266status_t EventThread::readyToRun() {
267    ALOGI("EventThread ready to run.");
268    return NO_ERROR;
269}
270
271void EventThread::dump(String8& result, char* buffer, size_t SIZE) const {
272    Mutex::Autolock _l(mLock);
273    result.appendFormat("VSYNC state: %s\n",
274            mDebugVsyncEnabled?"enabled":"disabled");
275    result.appendFormat("  soft-vsync: %s\n",
276            mUseSoftwareVSync?"enabled":"disabled");
277    result.appendFormat("  numListeners=%u,\n  events-delivered: %u\n",
278            mDisplayEventConnections.size(), mDeliveredEvents);
279    for (size_t i=0 ; i<mDisplayEventConnections.size() ; i++) {
280        sp<Connection> connection =
281                mDisplayEventConnections.itemAt(i).promote();
282        result.appendFormat("    %p: count=%d\n",
283                connection.get(), connection!=NULL ? connection->count : 0);
284    }
285}
286
287// ---------------------------------------------------------------------------
288
289EventThread::Connection::Connection(
290        const sp<EventThread>& eventThread)
291    : count(-1), mEventThread(eventThread), mChannel(new BitTube())
292{
293}
294
295EventThread::Connection::~Connection() {
296    mEventThread->unregisterDisplayEventConnection(this);
297}
298
299void EventThread::Connection::onFirstRef() {
300    // NOTE: mEventThread doesn't hold a strong reference on us
301    mEventThread->registerDisplayEventConnection(this);
302}
303
304sp<BitTube> EventThread::Connection::getDataChannel() const {
305    return mChannel;
306}
307
308void EventThread::Connection::setVsyncRate(uint32_t count) {
309    mEventThread->setVsyncRate(count, this);
310}
311
312void EventThread::Connection::requestNextVsync() {
313    mEventThread->requestNextVsync(this);
314}
315
316status_t EventThread::Connection::postEvent(
317        const DisplayEventReceiver::Event& event) {
318    ssize_t size = DisplayEventReceiver::sendEvents(mChannel, &event, 1);
319    return size < 0 ? status_t(size) : status_t(NO_ERROR);
320}
321
322// ---------------------------------------------------------------------------
323
324}; // namespace android
325