rtc: rx8025: implement RX-8035 support

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 <matt@traverse.com.au>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210709044518.28769-2-matt@traverse.com.au

Author: mcbridematt

drivers/rtc/rtc-rx8025.c

@@ -60,14 +60,23 @@
 #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 i2c_device_id 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 model;
 	u8 ctrl1;
 };
 
@@ -100,10 +109,26 @@ 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 +142,8 @@ static int rx8025_check_validity(struct device *dev)
 		return -EINVAL;
 	}
 
-	if (!(ctrl2 & RX8025_BIT_CTRL2_XST)) {
+	xstp = rx8025_is_osc_stopped(drvdata->model, ctrl2);
+	if (xstp) {
 		dev_warn(dev, "crystal stopped, date is invalid\n");
 		return -EINVAL;
 	}
@@ -127,29 +153,36 @@ static int rx8025_check_validity(struct device *dev)
 
 static int rx8025_reset_validity(struct i2c_client *client)
 {
+	struct rx8025_data *drvdata = i2c_get_clientdata(client);
 	int ctrl2 = rx8025_read_reg(client, RX8025_REG_CTRL2);
 
 	if (ctrl2 < 0)
 		return ctrl2;
 
 	ctrl2 &= ~(RX8025_BIT_CTRL2_PON | RX8025_BIT_CTRL2_VDET);
 
+	if (drvdata->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)
 {
 	struct i2c_client *client = dev_id;
 	struct rx8025_data *rx8025 = i2c_get_clientdata(client);
-	int status;
+	int status, xstp;
 
 	rtc_lock(rx8025->rtc);
 	status = rx8025_read_reg(client, RX8025_REG_CTRL2);
 	if (status < 0)
 		goto out;
 
-	if (!(status & RX8025_BIT_CTRL2_XST))
+	xstp = rx8025_is_osc_stopped(rx8025->model, status);
+	if (xstp)
 		dev_warn(&client->dev, "Oscillation stop was detected,"
 			 "you may have to readjust the clock\n");
 
@@ -519,6 +552,9 @@ static int rx8025_probe(struct i2c_client *client,
 
 	i2c_set_clientdata(client, rx8025);
 
+	if (id)
+		rx8025->model = id->driver_data;
+
 	err = rx8025_init_client(client);
 	if (err)
 		return err;