[PATCH] rtc: pcf8523: properly handle oscillator stop bit

[Alexandre Belloni]

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.bell...@free-electrons.com>
---
 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, &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);
-- 
2.7.0