sc16is7xx: Add flag to activate IrDA mode

This series of uart controllers is able to work in IrDA mode.
Add per-port flag to the device-tree to enable that feature if needed.

Signed-off-by: Pascal Huerst <pascal.huerst@gmail.com>
Signed-off-by: Daniel Mack <daniel@zonque.org>
Link: https://lore.kernel.org/r/20200529055058.1606910-3-daniel@zonque.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sc16is7xx.c

@@ -315,6 +315,7 @@ struct sc16is7xx_one {
 	struct kthread_work		tx_work;
 	struct kthread_work		reg_work;
 	struct sc16is7xx_one_config	config;
+	bool				irda_mode;
 };
 
 struct sc16is7xx_port {
@@ -986,6 +987,7 @@ static int sc16is7xx_config_rs485(struct uart_port *port,
 
 static int sc16is7xx_startup(struct uart_port *port)
 {
+	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	unsigned int val;
 
@@ -1024,6 +1026,13 @@ static int sc16is7xx_startup(struct uart_port *port)
 	/* Now, initialize the UART */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, SC16IS7XX_LCR_WORD_LEN_8);
 
+	/* Enable IrDA mode if requested in DT */
+	/* This bit must be written with LCR[7] = 0 */
+	sc16is7xx_port_update(port, SC16IS7XX_MCR_REG,
+			      SC16IS7XX_MCR_IRDA_BIT,
+			      one->irda_mode ?
+				SC16IS7XX_MCR_IRDA_BIT : 0);
+
 	/* Enable the Rx and Tx FIFO */
 	sc16is7xx_port_update(port, SC16IS7XX_EFCR_REG,
 			      SC16IS7XX_EFCR_RXDISABLE_BIT |
@@ -1304,6 +1313,17 @@ static int sc16is7xx_probe(struct device *dev,
 		sc16is7xx_power(&s->p[i].port, 0);
 	}
 
+	if (dev->of_node) {
+		struct property *prop;
+		const __be32 *p;
+		u32 u;
+
+		of_property_for_each_u32(dev->of_node, "irda-mode-ports",
+					 prop, p, u)
+			if (u < devtype->nr_uart)
+				s->p[u].irda_mode = true;
+	}
+
 	/*
 	 * Setup interrupt. We first try to acquire the IRQ line as level IRQ.
 	 * If that succeeds, we can allow sharing the interrupt as well.