[rtc-linux] [PATCH 1/2] RTC: s35390a: handle invalid RTC time

[Fabien Lahoudere <fabien.lahoudere@collabora.co.uk>]

If RTC time have been altered by low voltage, we notify users
that RTC time is invalid by returning -EINVAL.
The RTC time needs to be set correctly to clear the invalid flag.
If the RTC is not set before restarting, the information will be lost.

Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.co.uk>
---
 drivers/rtc/rtc-s35390a.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/rtc/rtc-s35390a.c b/drivers/rtc/rtc-s35390a.c
index 5dab466..ef4ada9 100644
--- a/drivers/rtc/rtc-s35390a.c
+++ b/drivers/rtc/rtc-s35390a.c
@@ -62,6 +62,7 @@ struct s35390a {
 	struct i2c_client *client[8];
 	struct rtc_device *rtc;
 	int twentyfourhour;
+	int isinvalid;
 };
 
 static int s35390a_set_reg(struct s35390a *s35390a, int reg, char *buf, int len)
@@ -135,6 +136,8 @@ static int s35390a_reset(struct s35390a *s35390a, char *status1)
 	 * The 24H bit is kept over reset, so set it already here.
 	 */
 initialize:
+	/* set the RTC time as invalid */
+	s35390a->isinvalid = 1;
 	*status1 = S35390A_FLAG_24H;
 	buf = S35390A_FLAG_RESET | S35390A_FLAG_24H;
 	ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
@@ -221,6 +224,8 @@ static int s35390a_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 		buf[i] = bitrev8(buf[i]);
 
 	err = s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
+	if (err >= 0)
+		s35390a->isinvalid = 0;
 
 	return err;
 }
@@ -231,6 +236,9 @@ static int s35390a_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 	char buf[7];
 	int i, err;
 
+	if (s35390a->isinvalid)
+		return -EINVAL;
+
 	err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
 	if (err < 0)
 		return err;
@@ -418,6 +426,7 @@ static int s35390a_probe(struct i2c_client *client,
 
 	s35390a->client[0] = client;
 	i2c_set_clientdata(client, s35390a);
+	s35390a->isinvalid = 0;
 
 	/* This chip uses multiple addresses, use dummy devices for them */
 	for (i = 1; i < 8; ++i) {
-- 
1.8.3.1

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