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      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  */
     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  */
     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__)
     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  */
    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