1 /*
2 * Copyright (C) 2008 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
18 /*
19 * System clock functions.
20 */
21
22 #if defined(__ANDROID__)
23 #include <linux/ioctl.h>
24 #include <linux/rtc.h>
25 #include <utils/Atomic.h>
26 #include <linux/android_alarm.h>
27 #endif
28
29 #include <sys/time.h>
30 #include <limits.h>
31 #include <fcntl.h>
32 #include <string.h>
33
34 #include <utils/SystemClock.h>
35 #include <utils/Timers.h>
36
37 #define LOG_TAG "SystemClock"
38 #include <utils/Log.h>
39
40 namespace android {
41
42 /*
43 * native public static long uptimeMillis();
44 */
uptimeMillis()45 int64_t uptimeMillis()
46 {
47 int64_t when = systemTime(SYSTEM_TIME_MONOTONIC);
48 return (int64_t) nanoseconds_to_milliseconds(when);
49 }
50
51 /*
52 * native public static long elapsedRealtime();
53 */
elapsedRealtime()54 int64_t elapsedRealtime()
55 {
56 return nanoseconds_to_milliseconds(elapsedRealtimeNano());
57 }
58
59 #define METHOD_CLOCK_GETTIME 0
60 #define METHOD_IOCTL 1
61 #define METHOD_SYSTEMTIME 2
62
63 /*
64 * To debug/verify the timestamps returned by the kernel, change
65 * DEBUG_TIMESTAMP to 1 and call the timestamp routine from a single thread
66 * in the test program. b/10899829
67 */
68 #define DEBUG_TIMESTAMP 0
69
70 #if DEBUG_TIMESTAMP && defined(__arm__)
checkTimeStamps(int64_t timestamp,int64_t volatile * prevTimestampPtr,int volatile * prevMethodPtr,int curMethod)71 static inline void checkTimeStamps(int64_t timestamp,
72 int64_t volatile *prevTimestampPtr,
73 int volatile *prevMethodPtr,
74 int curMethod)
75 {
76 /*
77 * Disable the check for SDK since the prebuilt toolchain doesn't contain
78 * gettid, and int64_t is different on the ARM platform
79 * (ie long vs long long).
80 */
81 int64_t prevTimestamp = *prevTimestampPtr;
82 int prevMethod = *prevMethodPtr;
83
84 if (timestamp < prevTimestamp) {
85 static const char *gettime_method_names[] = {
86 "clock_gettime",
87 "ioctl",
88 "systemTime",
89 };
90
91 ALOGW("time going backwards: prev %lld(%s) vs now %lld(%s), tid=%d",
92 prevTimestamp, gettime_method_names[prevMethod],
93 timestamp, gettime_method_names[curMethod],
94 gettid());
95 }
96 // NOTE - not atomic and may generate spurious warnings if the 64-bit
97 // write is interrupted or not observed as a whole.
98 *prevTimestampPtr = timestamp;
99 *prevMethodPtr = curMethod;
100 }
101 #else
102 #define checkTimeStamps(timestamp, prevTimestampPtr, prevMethodPtr, curMethod)
103 #endif
104
105 /*
106 * native public static long elapsedRealtimeNano();
107 */
elapsedRealtimeNano()108 int64_t elapsedRealtimeNano()
109 {
110 #if defined(__ANDROID__)
111 struct timespec ts;
112 int result;
113 int64_t timestamp;
114 #if DEBUG_TIMESTAMP
115 static volatile int64_t prevTimestamp;
116 static volatile int prevMethod;
117 #endif
118
119 static int s_fd = -1;
120
121 if (s_fd == -1) {
122 int fd = open("/dev/alarm", O_RDONLY);
123 if (android_atomic_cmpxchg(-1, fd, &s_fd)) {
124 close(fd);
125 }
126 }
127
128 result = ioctl(s_fd,
129 ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
130
131 if (result == 0) {
132 timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
133 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod, METHOD_IOCTL);
134 return timestamp;
135 }
136
137 // /dev/alarm doesn't exist, fallback to CLOCK_BOOTTIME
138 result = clock_gettime(CLOCK_BOOTTIME, &ts);
139 if (result == 0) {
140 timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
141 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
142 METHOD_CLOCK_GETTIME);
143 return timestamp;
144 }
145
146 // XXX: there was an error, probably because the driver didn't
147 // exist ... this should return
148 // a real error, like an exception!
149 timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
150 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
151 METHOD_SYSTEMTIME);
152 return timestamp;
153 #else
154 return systemTime(SYSTEM_TIME_MONOTONIC);
155 #endif
156 }
157
158 }; // namespace android
159