i.MX6Q UART5 CTS as input

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i.MX6Q UART5 CTS as input

Contributor I

How shall UART5 be configured for correct operation with RTS/CTS?

As on the SABRESDB board where an external Bluetooth device can be connected to UART5, I have a device connected.

The device has a RTS output connected to iMX6 KEY_ROW4 where this iMX pin should operate as input.

For my Linux kernel I have a DTS configuration like this:

&iomuxc {

    uart5 {

        pinctrl_uart5_1: uart5grp-1 {

            fsl,pins = <

                MX6QDL_PAD_KEY_ROW4__UART5_CTS_B 0x1b0b1  /* UART5_CTS */

                MX6QDL_PAD_KEY_COL4__UART5_RTS_B 0x1b0b1  /* UART5_RTS */





&uart5 {

    compatible = "fsl,imx6q-uart", "fsl,imx21-uart";

    pinctrl-names = "default";

           pinctrl-0 = <&pinctrl_uart5_1>;



    status = "okay";


This configuration makes the KEY_ROW4 pad as output which collides with the RTS output from the external device.

If I understand the iMX6 reference manual correct this is also the case since UART5 is in DCE mode default.

Therefore I have also added "fsl,dte-mode" as above and uncommented it. No difference.

How shall I configure the DTS for appropriate function (input) on the KEY_ROW4 pad?

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NXP TechSupport
NXP TechSupport

in the linux/arch/arm/mach-mx6/serial.h, the flow control of UART5 may be disabled by default. Please enable the flow control in the serial.h

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