rtc: m41t62: add oscillator fail bit reset support

In case of empty battery or glitches the oscillator fail
bit might be set. This will reset the bit in the reset
routine.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/drivers/rtc/m41t62.c b/drivers/rtc/m41t62.c
index 85d6eb02593fb74f86e94b1e3fd6c2ef1d92fdc2..0a4e12d69827d303261783c7360cbbe51bfe5ec7 100644 (file)
--- a/drivers/rtc/m41t62.c
+++ b/drivers/rtc/m41t62.c
@@ -23,6 +23,7 @@
 #include <rtc.h>
 #include <i2c.h>
 #include <linux/log2.h>
+#include <linux/delay.h>
 
 #define M41T62_REG_SSEC        0
 #define M41T62_REG_SEC 1
@@ -48,6 +49,7 @@
 #define M41T62_ALMON_SQWE      (1 << 6)        /* SQWE: SQW Enable Bit */
 #define M41T62_ALHOUR_HT       (1 << 6)        /* HT: Halt Update Bit */
 #define M41T62_FLAGS_AF                (1 << 6)        /* AF: Alarm Flag Bit */
+#define M41T62_FLAGS_OF                (1 << 2)        /* OF: Oscillator Flag Bit */
 #define M41T62_FLAGS_BATT_LOW  (1 << 4)        /* BL: Battery Low Bit */
 
 #define M41T62_WDAY_SQW_FREQ_MASK      0xf0
@@ -193,6 +195,50 @@ static int m41t62_sqw_set_rate(struct udevice *dev, unsigned int rate)
        return dm_i2c_write(dev, M41T62_REG_WDAY, &newval, sizeof(newval));
 }
 
+static int m41t62_rtc_restart_osc(struct udevice *dev)
+{
+       u8 val;
+       int ret;
+
+       /* 0. check if oscillator failure happened */
+       ret = dm_i2c_read(dev, M41T62_REG_FLAGS, &val, sizeof(val));
+       if (ret)
+               return ret;
+       if (!(val & M41T62_FLAGS_OF))
+               return 0;
+
+       ret = dm_i2c_read(dev, M41T62_REG_SEC, &val, sizeof(val));
+       if (ret)
+               return ret;
+
+       /* 1. Set stop bit */
+       val |= M41T62_SEC_ST;
+       ret = dm_i2c_write(dev, M41T62_REG_ALARM_HOUR, &val, sizeof(val));
+       if (ret)
+               return ret;
+
+       /* 2. Clear stop bit */
+       val &= ~M41T62_SEC_ST;
+       ret = dm_i2c_write(dev, M41T62_REG_ALARM_HOUR, &val, sizeof(val));
+       if (ret)
+               return ret;
+
+       /* 3. wait 4 seconds */
+       mdelay(4000);
+
+       ret = dm_i2c_read(dev, M41T62_REG_FLAGS, &val, sizeof(val));
+       if (ret)
+               return ret;
+
+       /* 4. clear M41T62_FLAGS_OF bit */
+       val &= ~M41T62_FLAGS_OF;
+       ret = dm_i2c_write(dev, M41T62_REG_FLAGS, &val, sizeof(val));
+       if (ret)
+               return ret;
+
+       return 0;
+}
+
 static int m41t62_rtc_clear_ht(struct udevice *dev)
 {
        u8 val;
@@ -218,6 +264,10 @@ static int m41t62_rtc_reset(struct udevice *dev)
 {
        int ret;
 
+       ret = m41t62_rtc_restart_osc(dev);
+       if (ret)
+               return ret;
+
        ret = m41t62_rtc_clear_ht(dev);
        if (ret)
                return ret;