The RX-8035 is a newer RTC from EPSON that is very
similar to the RX-8025.

The key difference is in the oscillation stop (XSTP)
bit which is inverted on the RX-8035.

Signed-off-by: Mathew McBride <redacted>
---
 drivers/rtc/rtc-rx8025.c | 59 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-rx8025.c b/drivers/rtc/rtc-rx8025.c
index c914091819ba..1a33ec402f4a 100644
--- a/drivers/rtc/rtc-rx8025.c
+++ b/drivers/rtc/rtc-rx8025.c

@@ -60,14 +60,24 @@
 #define RX8025_ADJ_DATA_MAX    62
 #define RX8025_ADJ_DATA_MIN    -62

+enum rx_model {
+       model_rx_unknown,
+       model_rx_8025,
+       model_rx_8035,
+       model_last
+};
+
 static const struct d rx8025_id[] = {
-       { "rx8025", 0 },
+       { "rx8025", model_rx_8025 },
+       { "rx8035", model_rx_8035 },
        { }
 };
+
 MODULE_DEVICE_TABLE(i2c, rx8025_id);

 struct rx8025_data {
        struct rtc_device *rtc;
+       enum rx_model type;

        u8 ctrl1;
 };

@@ -100,10 +110,26 @@ static s32 rx8025_write_regs(const struct i2c_client *client,
                                              length, values);
 }

+static int rx8025_is_osc_stopped(enum rx_model model, int ctrl2)
+{
+       int xstp = ctrl2 & RX8025_BIT_CTRL2_XST;
+       /* XSTP bit has different polarity on RX-8025 vs RX-8035.
+        * RX-8025: 0 == oscillator stopped
+        * RX-8035: 1 == oscillator stopped
+        */
+
+       if (model == model_rx_8025)
+               xstp = !xstp;
+
+       return xstp;
+}
+
 static int rx8025_check_validity(struct device *dev)
 {
        struct i2c_client *client = to_i2c_client(dev);
+       struct rx8025_data *drvdata = dev_get_drvdata(dev);
        int ctrl2;
+       int xstp;

        ctrl2 = rx8025_read_reg(client, RX8025_REG_CTRL2);
        if (ctrl2 < 0)

@@ -117,7 +143,8 @@ static int rx8025_check_validity(struct device *dev)
                return -EINVAL;
        }

-       if (!(ctrl2 & RX8025_BIT_CTRL2_XST)) {
+       xstp = rx8025_is_osc_stopped(drvdata->type, ctrl2);
+       if (xstp) {
                dev_warn(dev, "crystal stopped, date is invalid\n");
                return -EINVAL;
        }

@@ -125,7 +152,7 @@ static int rx8025_check_validity(struct device *dev)
        return 0;
 }

-static int rx8025_reset_validity(struct i2c_client *client)
+static int rx8025_reset_validity(enum rx_model model, struct i2c_client *client)

 {
        int ctrl2 = rx8025_read_reg(client, RX8025_REG_CTRL2);

@@ -134,8 +161,13 @@ static int rx8025_reset_validity(struct i2c_client *client)

        ctrl2 &= ~(RX8025_BIT_CTRL2_PON | RX8025_BIT_CTRL2_VDET);

+       if (model == model_rx_8025)
+               ctrl2 |= RX8025_BIT_CTRL2_XST;
+       else
+               ctrl2 &= ~(RX8025_BIT_CTRL2_XST);
+
        return rx8025_write_reg(client, RX8025_REG_CTRL2,
-                               ctrl2 | RX8025_BIT_CTRL2_XST);
+                               ctrl2);
 }

 static irqreturn_t rx8025_handle_irq(int irq, void *dev_id)

@@ -149,7 +181,7 @@ static irqreturn_t (int irq, void *dev_id)
        if (status < 0)
                goto out;

-       if (!(status & RX8025_BIT_CTRL2_XST))
+       if (rx8025_is_osc_stopped(rx8025->type, status))

                dev_warn(&client->dev, "Oscillation stop was detected,"
                         "you may have to readjust the clock\n");

@@ -241,7 +273,7 @@ static int rx8025_set_time(struct device *dev, struct rtc_time *dt)
        if (ret < 0)
                return ret;

-       return rx8025_reset_validity(client);
+       return rx8025_reset_validity(rx8025->type, client);
 }

 static int rx8025_init_client(struct i2c_client *client)

@@ -519,6 +551,21 @@ static int rx8025_probe(struct i2c_client *client,

        i2c_set_clientdata(client, rx8025);

+       if (id) {
+               rx8025->type = id->driver_data;
+               switch (rx8025->type) {
+               case model_rx_8025:
+                       dev_info(&client->dev, "Type RX-8025");
+               break;