can: tcan4x5x: tcan4x5x_parse_config(): Disable the INH pin device-state GPIO is unavailable

If the device state GPIO is not connected to the host then disable the
INH output from the TCAN device per section 8.3.5 of the data sheet.
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/tcan4x5x.c

@@ -102,6 +102,7 @@
 #define TCAN4X5X_MODE_NORMAL BIT(7)
 
 #define TCAN4X5X_DISABLE_WAKE_MSK	(BIT(31) | BIT(30))
+#define TCAN4X5X_DISABLE_INH_MSK	BIT(9)
 
 #define TCAN4X5X_SW_RESET BIT(2)
 
@@ -370,6 +371,14 @@ static int tcan4x5x_disable_wake(struct m_can_classdev *cdev)
 				  TCAN4X5X_DISABLE_WAKE_MSK, 0x00);
 }
 
+static int tcan4x5x_disable_state(struct m_can_classdev *cdev)
+{
+	struct tcan4x5x_priv *tcan4x5x = cdev->device_data;
+
+	return regmap_update_bits(tcan4x5x->regmap, TCAN4X5X_CONFIG,
+				  TCAN4X5X_DISABLE_INH_MSK, 0x01);
+}
+
 static int tcan4x5x_parse_config(struct m_can_classdev *cdev)
 {
 	struct tcan4x5x_priv *tcan4x5x = cdev->device_data;
@@ -396,8 +405,10 @@ static int tcan4x5x_parse_config(struct m_can_classdev *cdev)
 	tcan4x5x->device_state_gpio = devm_gpiod_get_optional(cdev->dev,
 							      "device-state",
 							      GPIOD_IN);
-	if (IS_ERR(tcan4x5x->device_state_gpio))
+	if (IS_ERR(tcan4x5x->device_state_gpio)) {
 		tcan4x5x->device_state_gpio = NULL;
+		tcan4x5x_disable_state(cdev);
+	}
 
 	return 0;
 }