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rtc: pcf8523: properly handle oscillator stop bit

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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 <alexandre.belloni@free-electrons.com>
This commit is contained in:
Alexandre Belloni 2016-03-03 09:55:47 +01:00
parent 2da424af45
commit ede44c908d
1 changed files with 3 additions and 22 deletions
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25
drivers/rtc/rtc-pcf8523.c
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@ -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, &regs[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);