tty: serial: lpuart: Disable transmitter on setting modem register

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>

1 files changed, 51 insertions, 20 deletions

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 36baca0ee12e..3d19bcbfff47 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1213,6 +1213,48 @@ static inline void lpuart_prepare_rx(struct lpuart_port *sport)
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
+static void lpuart_setup_rs485(struct lpuart_port *sport)
+{
+	/* Todo implement for 8-bit registers */
+}
+
+static void lpuart32_setup_rs485(struct lpuart_port *sport)
+{
+	struct serial_rs485 *rs485 = &sport->port.rs485;
+	unsigned long val, ctrl, ctrl_saved;
+
+	val = lpuart32_read(&sport->port, UARTMODIR) &
+			~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE);
+
+	/* Make sure transmitter is disabled */
+	ctrl = lpuart32_read(&sport->port, UARTCTRL);
+	ctrl_saved = ctrl;
+	ctrl &= ~(UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_TE |
+			UARTCTRL_RIE | UARTCTRL_RE);
+	lpuart32_write(&sport->port, ctrl, UARTCTRL);
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* Enable auto RS-485 RTS mode */
+		val |= UARTMODIR_TXRTSE;
+
+		/*
+		* The hardware defaults to RTS logic HIGH while transfer.
+		* Switch polarity in case RTS shall be logic HIGH
+		* after transfer.
+		* Note: UART is assumed to be active high.
+		*/
+		if (rs485->flags & SER_RS485_RTS_ON_SEND)
+			val &= ~UARTMODIR_TXRTSPOL;
+		else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
+			val |= UARTMODIR_TXRTSPOL;
+	}
+
+	lpuart32_write(&sport->port, val, UARTMODIR);
+
+	/* Restore cr2 */
+	lpuart32_write(&sport->port, ctrl_saved, UARTCTRL);
+}
+
 static int lpuart_config_rs485(struct uart_port *port,
 			struct serial_rs485 *rs485)
 {
@@ -1270,19 +1312,12 @@ static int lpuart32_config_rs485(struct uart_port *port,
 	struct lpuart_port *sport = container_of(port,
 			struct lpuart_port, port);
 
-	unsigned long modem = lpuart32_read(&sport->port, UARTMODIR)
-				& ~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE);
-	lpuart32_write(&sport->port, modem, UARTMODIR);
-
 	/* clear unsupported configurations */
 	rs485->delay_rts_before_send = 0;
 	rs485->delay_rts_after_send = 0;
 	rs485->flags &= ~SER_RS485_RX_DURING_TX;
 
 	if (rs485->flags & SER_RS485_ENABLED) {
-		/* Enable auto RS-485 RTS mode */
-		modem |= UARTMODIR_TXRTSE;
-
 		/*
 		 * RTS needs to be logic HIGH either during transer _or_ after
 		 * transfer, other variants are not supported by the hardware.
@@ -1295,23 +1330,14 @@ static int lpuart32_config_rs485(struct uart_port *port,
 		if (rs485->flags & SER_RS485_RTS_ON_SEND &&
 				rs485->flags & SER_RS485_RTS_AFTER_SEND)
 			rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
-
-		/*
-		 * The hardware defaults to RTS logic HIGH while transfer.
-		 * Switch polarity in case RTS shall be logic HIGH
-		 * after transfer.
-		 * Note: UART is assumed to be active high.
-		 */
-		if (rs485->flags & SER_RS485_RTS_ON_SEND)
-			modem &= ~UARTMODIR_TXRTSPOL;
-		else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
-			modem |= UARTMODIR_TXRTSPOL;
 	}
 
 	/* Store the new configuration */
 	sport->port.rs485 = *rs485;
 
-	lpuart32_write(&sport->port, modem, UARTMODIR);
+	/* config_rs485 gets called in irqsave context so do not lock again */
+	lpuart32_setup_rs485(sport);
+
 	return 0;
 }
 
@@ -1629,6 +1655,7 @@ static int lpuart32_startup(struct uart_port *port)
 
 	spin_lock_irqsave(&sport->port.lock, flags);
 
+	lpuart32_setup_rs485(sport);
 	lpuart32_setup_watermark(sport);
 
 	temp = lpuart32_read(&sport->port, UARTCTRL);
@@ -2490,7 +2517,7 @@ static int lpuart_probe(struct platform_device *pdev)
 	struct device_node *np = pdev->dev.of_node;
 	struct lpuart_port *sport;
 	struct resource *res;
-	unsigned long cr_32;
+	unsigned long cr_32, flags;
 	unsigned char cr_8;
 	int ret;
 
@@ -2616,7 +2643,10 @@ static int lpuart_probe(struct platform_device *pdev)
 	if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time")) {
 		sport->port.rs485.flags |= SER_RS485_ENABLED;
 		sport->port.rs485.flags |= SER_RS485_RTS_ON_SEND;
+
+		spin_lock_irqsave(&sport->port.lock, flags);
 		sport->port.rs485_config(&sport->port, &sport->port.rs485);
+		spin_unlock_irqrestore(&sport->port.lock, flags);
 	}
 
 	return 0;
@@ -2854,6 +2884,7 @@ static inline void lpuart32_resume_init(struct lpuart_port *sport)
 	unsigned long flags;
 
 	spin_lock_irqsave(&sport->port.lock, flags);
+	lpuart32_setup_rs485(sport);
 	lpuart32_setup_watermark(sport);
 
 	temp = lpuart32_read(&sport->port, UARTCTRL);