rtc: abx80x: handle the oscillator failure bit

Handle the Oscillator Failure ('OF') bit from Oscillator Status register
(0x1D). This bit is cleared on set_time function and is read each time the
date/time is read, but only in case of XT Oscillator selection.
In RC mode, this bit is always set.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

1 files changed, 31 insertions, 2 deletions

diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
index 0e4c9a0989d1..ba0d61934d35 100644
--- a/drivers/rtc/rtc-abx80x.c
+++ b/drivers/rtc/rtc-abx80x.c
@@ -58,6 +58,7 @@
 #define ABX8XX_OSC_OSEL         BIT(7)
 
 #define ABX8XX_REG_OSS          0x1d
+#define ABX8XX_OSS_OF           BIT(1)
 #define ABX8XX_OSS_OMODE        BIT(4)
 
 #define ABX8XX_REG_CFG_KEY      0x1f
@@ -138,7 +139,23 @@ static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
         struct i2c_client *client = to_i2c_client(dev);
         unsigned char buf[8];
-        int err;
+        int err, flags, rc_mode = 0;
+
+        /* Read the Oscillator Failure only in XT mode */
+        rc_mode = abx80x_is_rc_mode(client);
+        if (rc_mode < 0)
+                return rc_mode;
+
+        if (!rc_mode) {
+                flags = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSS);
+                if (flags < 0)
+                        return flags;
+
+                if (flags & ABX8XX_OSS_OF) {
+                        dev_err(dev, "Oscillator failure, data is invalid.\n");
+                        return -EINVAL;
+                }
+        }
 
         err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_HTH,
                                             sizeof(buf), buf);
@@ -166,7 +183,7 @@ static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
         struct i2c_client *client = to_i2c_client(dev);
         unsigned char buf[8];
-        int err;
+        int err, flags;
 
         if (tm->tm_year < 100)
                 return -EINVAL;
@@ -187,6 +204,18 @@ static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
                 return -EIO;
         }
 
+        /* Clear the OF bit of Oscillator Status Register */
+        flags = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSS);
+        if (flags < 0)
+                return flags;
+
+        err = i2c_smbus_write_byte_data(client, ABX8XX_REG_OSS,
+                                        flags & ~ABX8XX_OSS_OF);
+        if (err < 0) {
+                dev_err(&client->dev, "Unable to write oscillator status register\n");
+                return err;
+        }
+
         return 0;
 }