diff options
Diffstat (limited to 'drivers/rtc')
| -rw-r--r-- | drivers/rtc/class.c | 65 |
1 files changed, 48 insertions, 17 deletions
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index 4194e59e14cd..01a7df5317c1 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -41,20 +41,41 @@ static void rtc_device_release(struct device *dev) * system's wall clock; restore it on resume(). */ -static time_t oldtime; -static struct timespec oldts; +static struct timespec old_rtc, old_system, old_delta; + static int rtc_suspend(struct device *dev, pm_message_t mesg) { struct rtc_device *rtc = to_rtc_device(dev); struct rtc_time tm; - + struct timespec delta, delta_delta; if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0) return 0; + /* snapshot the current RTC and system time at suspend*/ rtc_read_time(rtc, &tm); - ktime_get_ts(&oldts); - rtc_tm_to_time(&tm, &oldtime); + getnstimeofday(&old_system); + rtc_tm_to_time(&tm, &old_rtc.tv_sec); + + + /* + * To avoid drift caused by repeated suspend/resumes, + * which each can add ~1 second drift error, + * try to compensate so the difference in system time + * and rtc time stays close to constant. + */ + delta = timespec_sub(old_system, old_rtc); + delta_delta = timespec_sub(delta, old_delta); + if (abs(delta_delta.tv_sec) >= 2) { + /* + * if delta_delta is too large, assume time correction + * has occured and set old_delta to the current delta. + */ + old_delta = delta; + } else { + /* Otherwise try to adjust old_system to compensate */ + old_system = timespec_sub(old_system, delta_delta); + } return 0; } @@ -63,32 +84,42 @@ static int rtc_resume(struct device *dev) { struct rtc_device *rtc = to_rtc_device(dev); struct rtc_time tm; - time_t newtime; - struct timespec time; - struct timespec newts; + struct timespec new_system, new_rtc; + struct timespec sleep_time; if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0) return 0; - ktime_get_ts(&newts); + /* snapshot the current rtc and system time at resume */ + getnstimeofday(&new_system); rtc_read_time(rtc, &tm); if (rtc_valid_tm(&tm) != 0) { pr_debug("%s: bogus resume time\n", dev_name(&rtc->dev)); return 0; } - rtc_tm_to_time(&tm, &newtime); - if (newtime <= oldtime) { - if (newtime < oldtime) + rtc_tm_to_time(&tm, &new_rtc.tv_sec); + new_rtc.tv_nsec = 0; + + if (new_rtc.tv_sec <= old_rtc.tv_sec) { + if (new_rtc.tv_sec < old_rtc.tv_sec) pr_debug("%s: time travel!\n", dev_name(&rtc->dev)); return 0; } - /* calculate the RTC time delta */ - set_normalized_timespec(&time, newtime - oldtime, 0); - /* subtract kernel time between rtc_suspend to rtc_resume */ - time = timespec_sub(time, timespec_sub(newts, oldts)); + /* calculate the RTC time delta (sleep time)*/ + sleep_time = timespec_sub(new_rtc, old_rtc); + + /* + * Since these RTC suspend/resume handlers are not called + * at the very end of suspend or the start of resume, + * some run-time may pass on either sides of the sleep time + * so subtract kernel run-time between rtc_suspend to rtc_resume + * to keep things accurate. + */ + sleep_time = timespec_sub(sleep_time, + timespec_sub(new_system, old_system)); - timekeeping_inject_sleeptime(&time); + timekeeping_inject_sleeptime(&sleep_time); return 0; } |