rtc: s35390a: handle invalid RTC time

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.

Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.co.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

diff --git a/drivers/rtc/rtc-s35390a.c b/drivers/rtc/rtc-s35390a.c
index 449820e..3aec3b2 100644 (file)
--- a/drivers/rtc/rtc-s35390a.c
+++ b/drivers/rtc/rtc-s35390a.c
@@ -106,33 +106,12 @@ static int s35390a_get_reg(struct s35390a *s35390a, int reg, char *buf, int len)
        return 0;
 }
 
-/*
- * Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
- * To keep the information if an irq is pending, pass the value read from
- * STATUS1 to the caller.
- */
-static int s35390a_reset(struct s35390a *s35390a, char *status1)
+static int s35390a_init(struct s35390a *s35390a)
 {
        char buf;
        int ret;
        unsigned initcount = 0;
 
-       ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
-       if (ret < 0)
-               return ret;
-
-       if (*status1 & S35390A_FLAG_POC)
-               /*
-                * Do not communicate for 0.5 seconds since the power-on
-                * detection circuit is in operation.
-                */
-               msleep(500);
-       else if (!(*status1 & S35390A_FLAG_BLD))
-               /*
-                * If both POC and BLD are unset everything is fine.
-                */
-               return 0;
-
        /*
         * At least one of POC and BLD are set, so reinitialise chip. Keeping
         * this information in the hardware to know later that the time isn't
@@ -142,7 +121,6 @@ static int s35390a_reset(struct s35390a *s35390a, char *status1)
         * The 24H bit is kept over reset, so set it already here.
         */
 initialize:
-       *status1 = S35390A_FLAG_24H;
        buf = S35390A_FLAG_RESET | S35390A_FLAG_24H;
        ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
 
@@ -165,6 +143,34 @@ initialize:
        return 1;
 }
 
+/*
+ * Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
+ * To keep the information if an irq is pending, pass the value read from
+ * STATUS1 to the caller.
+ */
+static int s35390a_read_status(struct s35390a *s35390a, char *status1)
+{
+       int ret;
+
+       ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
+       if (ret < 0)
+               return ret;
+
+       if (*status1 & S35390A_FLAG_POC) {
+               /*
+                * Do not communicate for 0.5 seconds since the power-on
+                * detection circuit is in operation.
+                */
+               msleep(500);
+               return 1;
+       } else if (*status1 & S35390A_FLAG_BLD)
+               return 1;
+       /*
+        * If both POC and BLD are unset everything is fine.
+        */
+       return 0;
+}
+
 static int s35390a_disable_test_mode(struct s35390a *s35390a)
 {
        char buf[1];
@@ -208,13 +214,16 @@ static int s35390a_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
        struct s35390a  *s35390a = i2c_get_clientdata(client);
        int i, err;
-       char buf[7];
+       char buf[7], status;
 
        dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d mday=%d, "
                "mon=%d, year=%d, wday=%d\n", __func__, tm->tm_sec,
                tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
                tm->tm_wday);
 
+       if (s35390a_read_status(s35390a, &status) == 1)
+               s35390a_init(s35390a);
+
        buf[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 100);
        buf[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon + 1);
        buf[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
@@ -235,9 +244,12 @@ static int s35390a_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 static int s35390a_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
        struct s35390a *s35390a = i2c_get_clientdata(client);
-       char buf[7];
+       char buf[7], status;
        int i, err;
 
+       if (s35390a_read_status(s35390a, &status) == 1)
+               return -EINVAL;
+
        err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
        if (err < 0)
                return err;
@@ -405,7 +417,7 @@ static struct i2c_driver s35390a_driver;
 static int s35390a_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
 {
-       int err, err_reset;
+       int err, err_read;
        unsigned int i;
        struct s35390a *s35390a;
        struct rtc_time tm;
@@ -438,9 +450,9 @@ static int s35390a_probe(struct i2c_client *client,
                }
        }
 
-       err_reset = s35390a_reset(s35390a, &status1);
-       if (err_reset < 0) {
-               err = err_reset;
+       err_read = s35390a_read_status(s35390a, &status1);
+       if (err_read < 0) {
+               err = err_read;
                dev_err(&client->dev, "error resetting chip\n");
                goto exit_dummy;
        }
@@ -466,7 +478,7 @@ static int s35390a_probe(struct i2c_client *client,
                }
        }
 
-       if (err_reset > 0 || s35390a_get_datetime(client, &tm) < 0)
+       if (err_read > 0 || s35390a_get_datetime(client, &tm) < 0)
                dev_warn(&client->dev, "clock needs to be set\n");
 
        device_set_wakeup_capable(&client->dev, 1);