rtc: abx80x: Configure reserved bits in RV1805

The RV1805 uses smaller package than the AB1805, discern those two
chips based on the compatible value and configure reserved bits in
the RV1805 to prevent current leakage and accidental test mode entry.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: linux-rtc@vger.kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-abx80x.c

@@ -46,6 +46,9 @@
 #define ABX8XX_CTRL_ARST	BIT(2)
 #define ABX8XX_CTRL_12_24	BIT(6)
 
+#define ABX8XX_REG_CTRL2	0x11
+#define ABX8XX_CTRL2_RSVD	BIT(5)
+
 #define ABX8XX_REG_IRQ		0x12
 #define ABX8XX_IRQ_AIE		BIT(2)
 #define ABX8XX_IRQ_IM_1_4	(0x3 << 5)
@@ -78,6 +81,9 @@
 
 #define ABX8XX_REG_ID0		0x28
 
+#define ABX8XX_REG_OUT_CTRL	0x30
+#define ABX8XX_OUT_CTRL_EXDS	BIT(4)
+
 #define ABX8XX_REG_TRICKLE	0x20
 #define ABX8XX_TRICKLE_CHARGE_ENABLE	0xa0
 #define ABX8XX_TRICKLE_STANDARD_DIODE	0x8
@@ -86,7 +92,7 @@
 static u8 trickle_resistors[] = {0, 3, 6, 11};
 
 enum abx80x_chip {AB0801, AB0803, AB0804, AB0805,
-	AB1801, AB1803, AB1804, AB1805, ABX80X};
+	AB1801, AB1803, AB1804, AB1805, RV1805, ABX80X};
 
 struct abx80x_cap {
 	u16 pn;
@@ -103,6 +109,7 @@ static struct abx80x_cap abx80x_caps[] = {
 	[AB1803] = {.pn = 0x1803},
 	[AB1804] = {.pn = 0x1804, .has_tc = true, .has_wdog = true},
 	[AB1805] = {.pn = 0x1805, .has_tc = true, .has_wdog = true},
+	[RV1805] = {.pn = 0x1805, .has_tc = true, .has_wdog = true},
 	[ABX80X] = {.pn = 0}
 };
 
@@ -723,6 +730,62 @@ static int abx80x_probe(struct i2c_client *client,
 		return -EIO;
 	}
 
+	/* Configure RV1805 specifics */
+	if (part == RV1805) {
+		/*
+		 * Avoid accidentally entering test mode. This can happen
+		 * on the RV1805 in case the reserved bit 5 in control2
+		 * register is set. RV-1805-C3 datasheet indicates that
+		 * the bit should be cleared in section 11h - Control2.
+		 */
+		data = i2c_smbus_read_byte_data(client, ABX8XX_REG_CTRL2);
+		if (data < 0) {
+			dev_err(&client->dev,
+				"Unable to read control2 register\n");
+			return -EIO;
+		}
+
+		err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CTRL2,
+						data & ~ABX8XX_CTRL2_RSVD);
+		if (err < 0) {
+			dev_err(&client->dev,
+				"Unable to write control2 register\n");
+			return -EIO;
+		}
+
+		/*
+		 * Avoid extra power leakage. The RV1805 uses smaller
+		 * 10pin package and the EXTI input is not present.
+		 * Disable it to avoid leakage.
+		 */
+		data = i2c_smbus_read_byte_data(client, ABX8XX_REG_OUT_CTRL);
+		if (data < 0) {
+			dev_err(&client->dev,
+				"Unable to read output control register\n");
+			return -EIO;
+		}
+
+		/*
+		 * Write the configuration key register to enable access to
+		 * the config2 register
+		 */
+		err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+						ABX8XX_CFG_KEY_MISC);
+		if (err < 0) {
+			dev_err(&client->dev,
+				"Unable to write configuration key\n");
+			return -EIO;
+		}
+
+		err = i2c_smbus_write_byte_data(client, ABX8XX_REG_OUT_CTRL,
+						data | ABX8XX_OUT_CTRL_EXDS);
+		if (err < 0) {
+			dev_err(&client->dev,
+				"Unable to write output control register\n");
+			return -EIO;
+		}
+	}
+
 	/* part autodetection */
 	if (part == ABX80X) {
 		for (i = 0; abx80x_caps[i].pn; i++)
@@ -826,7 +889,7 @@ static const struct i2c_device_id abx80x_id[] = {
 	{ "ab1803", AB1803 },
 	{ "ab1804", AB1804 },
 	{ "ab1805", AB1805 },
-	{ "rv1805", AB1805 },
+	{ "rv1805", RV1805 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, abx80x_id);