From ede44c908d44b166a5b6bd7caacd105c2ff5a70f Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Thu, 3 Mar 2016 09:55:47 +0100 Subject: [PATCH] rtc: pcf8523: properly handle oscillator stop bit The time and date register of the pcf8223 are undefined after a power reset. Properly handle the OS bit and return -EINVAL when that bit is set. It is properly removed when setting the time. This solves an issue where the time and date may be valid for rtc_valid_tm() but is not the current time. Signed-off-by: Alexandre Belloni --- drivers/rtc/rtc-pcf8523.c | 25 +++---------------------- 1 file changed, 3 insertions(+), 22 deletions(-) diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c index 988566caaaa6..28c48b3c1946 100644 --- a/drivers/rtc/rtc-pcf8523.c +++ b/drivers/rtc/rtc-pcf8523.c @@ -178,28 +178,8 @@ static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm) if (err < 0) return err; - if (regs[0] & REG_SECONDS_OS) { - /* - * If the oscillator was stopped, try to clear the flag. Upon - * power-up the flag is always set, but if we cannot clear it - * the oscillator isn't running properly for some reason. The - * sensible thing therefore is to return an error, signalling - * that the clock cannot be assumed to be correct. - */ - - regs[0] &= ~REG_SECONDS_OS; - - err = pcf8523_write(client, REG_SECONDS, regs[0]); - if (err < 0) - return err; - - err = pcf8523_read(client, REG_SECONDS, ®s[0]); - if (err < 0) - return err; - - if (regs[0] & REG_SECONDS_OS) - return -EAGAIN; - } + if (regs[0] & REG_SECONDS_OS) + return -EINVAL; tm->tm_sec = bcd2bin(regs[0] & 0x7f); tm->tm_min = bcd2bin(regs[1] & 0x7f); @@ -235,6 +215,7 @@ static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm) return err; regs[0] = REG_SECONDS; + /* This will purposely overwrite REG_SECONDS_OS */ regs[1] = bin2bcd(tm->tm_sec); regs[2] = bin2bcd(tm->tm_min); regs[3] = bin2bcd(tm->tm_hour); -- 2.20.1