Well, to summarize you have to compile the kernel 4.4: in the menu of the configuration, you switch to omap-serial.c with CONFIG_SERIAL_OMAP
and on the device tree you have to put something like :
&am33xx_pinmux {
…
uart1_pins: pinmux_uart1_pins {
pinctrl-single,pins = <
AM33XX_IOPAD(0x980, PIN_INPUT | MUX_MODE0) /* P9.26 uart1_rxd.uart1_rxd INPUT OK*/
AM33XX_IOPAD(0x984, PIN_OUTPUT | MUX_MODE0) /* P9.24 uart1_txd.uart1_txd OUTPUT OK*/
AM33XX_IOPAD(0x9a4, PIN_OUTPUT | MUX_MODE7) /* TX enable GPIO 3_19 OK*/
AM33XX_IOPAD(0x848, PIN_OUTPUT | MUX_MODE7) /* RX enable P9.14 GPIO 1_18 mode 7 OK*/
;
};
…
};
&uart1 {
pinctrl-names = “default”;
pinctrl-0 = <&uart1_pins>;
status = “okay”;
rts-gpio = <&gpio3 19 GPIO_ACTIVE_HIGH>; // 3_19
cts-gpio = <&gpio1 18 GPIO_ACTIVE_HIGH>; // 1_18
rs485-rts-active-high;
rs485-rts-delay = <0 0>;
linux,rs485-enabled-at-boot-time;
};
Enjoy !
Micka,