Thank you very much .
And I have made some changes on am335x-bone-common.dtsi according to what you told me.Followings are the changes I have made:
uart1_pins: pinmux_uart1_pins {
pinctrl-single,pins = <
0x74 (PIN_INPUT_PULLUP | MUX_MODE0) /* uart1_rxd.uart1_rxd gpio0_14 */
0x78 (PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* uart1_txd.uart1_txd gpio0_15*/
>;
};
uart2_pins: pinmux_uart2_pins {
pinctrl-single,pins = <
0x44 (PIN_INPUT_PULLUP | MUX_MODE1) /* uart2_rxd.uart2_rxd gpio0_2*/
0x48 (PIN_OUTPUT_PULLDOWN | MUX_MODE1) /* uart2_txd.uart2_txd gpio0_3*/
>;
};
uart4_pins: pinmux_uart4_pins {
pinctrl-single,pins = <
0xB4 (PIN_INPUT_PULLUP | MUX_MODE6) /* uart4_rxd.uart4_rxd gpio0_30*/
0xB8 (PIN_OUTPUT_PULLDOWN | MUX_MODE6) /* uart4_txd.uart4_txd gpio0_31 */
>;
};
uart1: serial@48022000 {
pinctrl-names = "default";
pinctrl-0 = <&uart1_pins>;
status = "okay";
};
uart2: serial@48024000 {
pinctrl-names = "default";
pinctrl-0 = <&uart2_pins>;
status = "okay";
};
uart4: serial@481a8000 {
pinctrl-names = "default";
pinctrl-0 = <&uart4_pins>;
status = "okay";
};
after compiling ,loading and rebooting ,i really can find ttyO1 ttyO2 ttyO4.
However,i doubt the changes what i have done are right or wrong.
Best regards~