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rtc: m41t62: add oscillator fail bit reset support

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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>
This commit is contained in:
Sebastian Reichel 2020-09-02 19:31:40 +02:00 committed by Stefano Babic
parent 8691198d1b
commit 9bbe210512
1 changed files with 50 additions and 0 deletions
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50
drivers/rtc/m41t62.c
View file

@ -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;