[PATCH 0/2] Implement support for inverted serial TX/RX on i.MX

[PATCH 0/2] Implement support for inverted serial TX/RX on i.MX

[George Hilliard]

This peripheral has dedicated control bits that flip input/output
signals before handing them off to the OS.  This is useful on my
hardware because the UART is connected to an RS-422 transceiver with the
+/- pins hooked up backward.  Instead of a hack flipping all the bits
before sending them, the hardware can do it for free.



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[PATCH 1/2] dt-bindings: serial: document fsl,inverted-tx and -rx options

[George Hilliard]

Add a description for the new fsl,inverted-tx and fsl,inverted-rx
options for the i.MX UART peripheral.

Signed-off-by: George Hilliard <ghilliard@kopismobile.com>
---
 Documentation/devicetree/bindings/serial/fsl-imx-uart.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt
index 35957cbf1571..c8d677f9491f 100644
--- a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt
+++ b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt
@@ -8,6 +8,10 @@ Required properties:
 Optional properties:
 - fsl,dte-mode : Indicate the uart works in DTE mode. The uart works
                   in DCE mode by default.
+- fsl,inverted-tx , fsl,inverted-rx : Indicate that the hardware attached
+  to the peripheral inverts the signal transmitted or received,
+  respectively, and that the peripheral should invert its output/input
+  using the INVT/INVR registers.
 - rs485-rts-delay, rs485-rts-active-low, rs485-rx-during-tx,
   linux,rs485-enabled-at-boot-time: see rs485.txt. Note that for RS485
   you must enable either the "uart-has-rtscts" or the "rts-gpios"
-- 
2.25.0


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

[George Hilliard]

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


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

[Uwe Kleine-König]

Hello George,

expanding Cc: a bit

On Mon, Feb 10, 2020 at 11:49:42AM -0600, George Hilliard wrote:
> 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.

Hmm, sad, I would have had some review feedback that should be addressed
before application of the patch. As I only noticed the footer after
looking at the patch, it was already too late to stop me reviewing it.
As I don't have an expressed permission I will at least not share it
(and I expect that Greg will also refuse to apply a patch with such a
footer).

:-|
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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

[George Hilliard]

On Mon, Feb 10, 2020 at 12:11 PM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> On Mon, Feb 10, 2020 at 11:49:42AM -0600, George Hilliard wrote:
> > (confidentiality spam)
>
> Hmm, sad, I would have had some review feedback that should be addressed
> before application of the patch. As I only noticed the footer after
> looking at the patch, it was already too late to stop me reviewing it.
> As I don't have an expressed permission I will at least not share it
> (and I expect that Greg will also refuse to apply a patch with such a
> footer).
>
This is fixed now. Apologies - added without my knowledge. Should I
simply resend a v2 without the notice?  Happy to CC everyone else you
included.

George

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

[Uwe Kleine-König]

Hi George,

On Mon, Feb 10, 2020 at 12:38:59PM -0600, George Hilliard wrote:
> On Mon, Feb 10, 2020 at 12:11 PM Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > On Mon, Feb 10, 2020 at 11:49:42AM -0600, George Hilliard wrote:
> > > (confidentiality spam)
> >
> > Hmm, sad, I would have had some review feedback that should be addressed
> > before application of the patch. As I only noticed the footer after
> > looking at the patch, it was already too late to stop me reviewing it.
> > As I don't have an expressed permission I will at least not share it
> > (and I expect that Greg will also refuse to apply a patch with such a
> > footer).
>
> This is fixed now. Apologies - added without my knowledge. Should I
> simply resend a v2 without the notice?  Happy to CC everyone else you
> included.

You did it right. (i.e. yes, resend without the notice is the right
thing.)

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |