You're welcome
How to setup:
This configuration is all done in the devicetree (arch/arm/boot/dts/armstonea9qdl.dtsi) in the node called &iomuxc and the subnodes there.
Have a look there to understand how it works.
To get UART4 you have to:
- create a new &uart4 node. See how it is done with the other uart nodes.
- create the &pinctrl_uart4_1 node with the 4 lines you have chosen above.
If there are other pinmux configurations for the pads you want to use you have to disable/uncomment these functions. This means there can't be a pinmux setting e.G. that is called: MX6QDL_PAD_CSI0_DAT12__GPIO5_IO30
Because we want to use the CSI0_DAT12 pad for the UART signal e.G. like this: MX6QDL_PAD_CSI0_DAT12__UART4_TX_DATA
For the pinctrl node you need 4 lines. These are the possibilities for the pins:
19
MX6QDL_PAD_CSI0_DAT12__UART4_TX_DATA
MX6QDL_PAD_CSI0_DAT12__UART4_RX_DATA
20
MX6QDL_PAD_CSI0_DAT13__UART4_RX_DATA
MX6QDL_PAD_CSI0_DAT13__UART4_TX_DATA
23
MX6QDL_PAD_CSI0_DAT16__UART4_RTS_B
MX6QDL_PAD_CSI0_DAT16__UART4_CTS_B
24
MX6QDL_PAD_CSI0_DAT17__UART4_CTS_B
MX6QDL_PAD_CSI0_DAT17__UART4_RTS_B
So you can decide if RX or TX should be on pin 19 or 20.
And on which of the pins 23, 24 RTS or CTS should be.
Best Regards
Your F&S Support Team