From 7dbfb315b2aaef0a115765946bf3026d074c33a7 Mon Sep 17 00:00:00 2001 From: Atsushi Nemoto Date: Tue, 21 Aug 2012 16:16:10 -0700 Subject: [PATCH] drivers/rtc/rtc-rs5c348.c: fix hour decoding in 12-hour mode Correct the offset by subtracting 20 from tm_hour before taking the modulo 12. [ "Why 20?" I hear you ask. Or at least I did. Here's the reason why: RS5C348_BIT_PM is 32, and is - stupidly - included in the RS5C348_HOURS_MASK define. So it's really subtracting out that bit to get "hour+12". But then because it does things modulo 12, it needs to add the 12 in again afterwards anyway. This code is confused. It would be much clearer if RS5C348_HOURS_MASK just didn't include the RS5C348_BIT_PM bit at all, then it wouldn't need to do the silly subtract either. Whatever. It's all just math, the end result is the same. - Linus ] Reported-by: James Nute Tested-by: James Nute Signed-off-by: Atsushi Nemoto Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/rtc/rtc-rs5c348.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/rtc/rtc-rs5c348.c b/drivers/rtc/rtc-rs5c348.c index 77074ccd2850..fd5c7af04ae5 100644 --- a/drivers/rtc/rtc-rs5c348.c +++ b/drivers/rtc/rtc-rs5c348.c @@ -122,9 +122,12 @@ rs5c348_rtc_read_time(struct device *dev, struct rtc_time *tm) tm->tm_min = bcd2bin(rxbuf[RS5C348_REG_MINS] & RS5C348_MINS_MASK); tm->tm_hour = bcd2bin(rxbuf[RS5C348_REG_HOURS] & RS5C348_HOURS_MASK); if (!pdata->rtc_24h) { - tm->tm_hour %= 12; - if (rxbuf[RS5C348_REG_HOURS] & RS5C348_BIT_PM) + if (rxbuf[RS5C348_REG_HOURS] & RS5C348_BIT_PM) { + tm->tm_hour -= 20; + tm->tm_hour %= 12; tm->tm_hour += 12; + } else + tm->tm_hour %= 12; } tm->tm_wday = bcd2bin(rxbuf[RS5C348_REG_WDAY] & RS5C348_WDAY_MASK); tm->tm_mday = bcd2bin(rxbuf[RS5C348_REG_DAY] & RS5C348_DAY_MASK); -- 2.30.2