[PATCH 7/8] serial: fsl_lpuart: add loopback support

[Michael Walle <michael@walle.cc>]

The LPUART can loop the RX and TX signal. Add support for it.

Please note, this was only tested on the 32 bit version of the LPUART.

Signed-off-by: Michael Walle <michael@walle.cc>
---
 drivers/tty/serial/fsl_lpuart.c | 36 +++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 19714047d571..5e66f628e895 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1403,22 +1403,54 @@ static int lpuart32_config_rs485(struct uart_port *port,
 
 static unsigned int lpuart_get_mctrl(struct uart_port *port)
 {
-	return 0;
+	unsigned int mctrl = 0;
+	u8 reg;
+
+	reg = readb(port->membase + UARTCR1);
+	if (reg & UARTCR1_LOOPS)
+		mctrl |= TIOCM_LOOP;
+
+	return mctrl;
 }
 
 static unsigned int lpuart32_get_mctrl(struct uart_port *port)
 {
-	return 0;
+	unsigned int mctrl = 0;
+	u32 reg;
+
+	reg = lpuart32_read(port, UARTCTRL);
+	if (reg & UARTCTRL_LOOPS)
+		mctrl |= TIOCM_LOOP;
+
+	return mctrl;
 }
 
 static void lpuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
+	u8 reg;
+
+	reg = readb(port->membase + UARTCR1);
+
+	/* for internal loopback we need LOOPS=1 and RSRC=0 */
+	reg &= ~(UARTCR1_LOOPS | UARTCR1_RSRC);
+	if (mctrl & TIOCM_LOOP)
+		reg |= UARTCR1_LOOPS;
 
+	writeb(reg, port->membase + UARTCR1);
 }
 
 static void lpuart32_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
+	u32 reg;
+
+	reg = lpuart32_read(port, UARTCTRL);
+
+	/* for internal loopback we need LOOPS=1 and RSRC=0 */
+	reg &= ~(UARTCTRL_LOOPS | UARTCTRL_RSRC);
+	if (mctrl & TIOCM_LOOP)
+		reg |= UARTCTRL_LOOPS;
 
+	lpuart32_write(port, reg, UARTCTRL);
 }
 
 static void lpuart_break_ctl(struct uart_port *port, int break_state)
-- 
2.20.1