[PATCH 2/2] tty: imx serial: Implement support for reversing TX and RX polarity

[George Hilliard <ghilliard@kopismobile.com>]

The peripheral has support for inverting its input and/or output
signals.  This is useful if the hardware flips polarity of the
peripheral's signal, such as swapped +/- pins on an RS-422 transceiver,
or an inverting level shifter.  Add support for these control registers
via the device tree binding.

Signed-off-by: George Hilliard <ghilliard@kopismobile.com>
---
 drivers/tty/serial/imx.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 0c6c63166250..467e78794997 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -195,6 +195,8 @@ struct imx_port {
 	unsigned int		have_rtscts:1;
 	unsigned int		have_rtsgpio:1;
 	unsigned int		dte_mode:1;
+	unsigned int		inverted_tx:1;
+	unsigned int		inverted_rx:1;
 	struct clk		*clk_ipg;
 	struct clk		*clk_per;
 	const struct imx_uart_data *devdata;
@@ -1335,7 +1337,7 @@ static int imx_uart_startup(struct uart_port *port)
 	int retval, i;
 	unsigned long flags;
 	int dma_is_inited = 0;
-	u32 ucr1, ucr2, ucr4;
+	u32 ucr1, ucr2, ucr3, ucr4;
 
 	retval = clk_prepare_enable(sport->clk_per);
 	if (retval)
@@ -1390,6 +1392,8 @@ static int imx_uart_startup(struct uart_port *port)
 	ucr4 = imx_uart_readl(sport, UCR4) & ~UCR4_OREN;
 	if (!sport->dma_is_enabled)
 		ucr4 |= UCR4_OREN;
+	if (sport->inverted_rx)
+		ucr4 |= UCR4_INVR;
 	imx_uart_writel(sport, ucr4, UCR4);
 
 	ucr2 = imx_uart_readl(sport, UCR2) & ~UCR2_ATEN;
@@ -1404,19 +1408,17 @@ static int imx_uart_startup(struct uart_port *port)
 		ucr2 &= ~UCR2_RTSEN;
 	imx_uart_writel(sport, ucr2, UCR2);
 
+	ucr3 = imx_uart_readl(sport, UCR3);
+	if (sport->inverted_tx)
+		ucr3 |= UCR3_INVT;
 	if (!imx_uart_is_imx1(sport)) {
-		u32 ucr3;
-
-		ucr3 = imx_uart_readl(sport, UCR3);
-
 		ucr3 |= UCR3_DTRDEN | UCR3_RI | UCR3_DCD;
 
 		if (sport->dte_mode)
 			/* disable broken interrupts */
 			ucr3 &= ~(UCR3_RI | UCR3_DCD);
-
-		imx_uart_writel(sport, ucr3, UCR3);
 	}
+	imx_uart_writel(sport, ucr3, UCR3);
 
 	/*
 	 * Enable modem status interrupts
@@ -2184,6 +2186,12 @@ static int imx_uart_probe_dt(struct imx_port *sport,
 	if (of_get_property(np, "rts-gpios", NULL))
 		sport->have_rtsgpio = 1;
 
+	if (of_get_property(np, "fsl,inverted-tx", NULL))
+		sport->inverted_tx = 1;
+
+	if (of_get_property(np, "fsl,inverted-rx", NULL))
+		sport->inverted_rx = 1;
+
 	return 0;
 }
 #else
-- 
2.25.0


-- 
CONFIDENTIALITY NOTICE: This email and any attachments are for the sole use 
of the intended recipient and may contain material that is proprietary, 
confidential, privileged or otherwise legally protected or restricted under 
applicable government laws. Any review, disclosure, distributing or other 
use without expressed permission of the sender is strictly prohibited. If 
you are not the intended recipient, please contact the sender and delete 
all copies without reading, printing, or saving.