From 65a84712596bfd5b0831b8a09691ad3eca391ade Mon Sep 17 00:00:00 2001 From: =?utf8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= Date: Fri, 25 Jul 2008 20:58:15 -0700 Subject: [PATCH] rtc: Try to prevent RTC errors from accumulating. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When we resume we only know how many whole seconds has elapsed. These errors would accumulate in delta. We now only set the delta if it would change by more than two seconds. If we drift back by by more than a second add one in resume. Signed-off-by: Arve Hjønnevåg --- drivers/rtc/class.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index be5a6b73e601..2bc9ef37b46f 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -40,25 +40,32 @@ static void rtc_device_release(struct device *dev) */ static struct timespec delta; +static struct timespec delta_delta; static time_t oldtime; 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 ts = current_kernel_time(); + struct timespec ts; + struct timespec new_delta; if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0) return 0; + getnstimeofday(&ts); rtc_read_time(rtc, &tm); rtc_tm_to_time(&tm, &oldtime); /* RTC precision is 1 second; adjust delta for avg 1/2 sec err */ - set_normalized_timespec(&delta, + set_normalized_timespec(&new_delta, ts.tv_sec - oldtime, ts.tv_nsec - (NSEC_PER_SEC >> 1)); + /* prevent 1/2 sec errors from accumulating */ + delta_delta = timespec_sub(new_delta, delta); + if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) + delta = new_delta; return 0; } @@ -78,6 +85,8 @@ static int rtc_resume(struct device *dev) return 0; } rtc_tm_to_time(&tm, &newtime); + if (delta_delta.tv_sec < -1) + newtime++; if (newtime <= oldtime) { if (newtime < oldtime) pr_debug("%s: time travel!\n", dev_name(&rtc->dev)); -- 2.34.1