From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
The VL bit in the seconds register remains set only until seconds are
written under main power. As this often happens during boot-up after
picking up a network time, make sure to preserve the low battery state
across this, caching it and returning it via the RTC_VL_BACKUP_LOW bit.
To permit userspace clearing this state during runtime, also implement
RTC_VL_CLR that works against the cached state.
This is emulating RTCs which have a battery voltage check that works
under main power as well.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
drivers/rtc/rtc-pcf8563.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 7e720472213c..f8c6cdb9a39d 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -81,6 +81,7 @@ struct pcf8563 {
#ifdef CONFIG_COMMON_CLK
struct clk_hw clkout_hw;
#endif
+ bool low_bat;
};
static int pcf8563_read_block_data(struct i2c_client *client, unsigned char reg,
@@ -207,6 +208,7 @@ static int pcf8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
return err;
if (buf[PCF8563_REG_SC] & PCF8563_SC_LV) {
+ pcf8563->low_bat = true;
dev_err(&client->dev,
"low voltage detected, date/time is not reliable.\n");
return -EINVAL;
@@ -277,6 +279,8 @@ static int pcf8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
static int pcf8563_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct pcf8563 *pcf8563 = i2c_get_clientdata(client);
+ unsigned int state = 0;
int ret;
switch (cmd) {
@@ -284,9 +288,16 @@ static int pcf8563_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long
ret = i2c_smbus_read_byte_data(client, PCF8563_REG_SC);
if (ret < 0)
return ret;
-
- return put_user(ret & PCF8563_SC_LV ? RTC_VL_DATA_INVALID : 0,
- (unsigned int __user *)arg);
+ if (ret & PCF8563_SC_LV) {
+ state |= RTC_VL_DATA_INVALID;
+ pcf8563->low_bat = true;
+ }
+ if (pcf8563->low_bat)
+ state |= RTC_VL_BACKUP_LOW;
+ return put_user(state, (unsigned int __user *)arg);
+ case RTC_VL_CLR:
+ pcf8563->low_bat = false;
+ return 0;
default:
return -ENOIOCTLCMD;
}
--
2.35.3
