OpenWrt使能mt7620a第二个uart

需要配置target/linux/ramips/dts/下相关文件（mt7620a.dtsi，MT7620a.dts）。

在mt7620a.dtsi中，palmbus@10000000下已经定义好了uart和uartlite，但是uart的status是disabled：

uart@500 {
compatible = "ralink,mt7620a-uart", "ralink,rt2880-uart", "ns16550a";
reg = <0x500 0x100>;
resets = <&rstctrl 12>;
reset-names = "uart";
interrupt-parent = <&intc>;
interrupts = <5>;
reg-shift = <2>;
status = "disabled";
};

在 pinctrl {中定义了uart各种复用的功能，但具体使用哪一种功能没有定义：

pcm_i2s_pins: pcm_i2s {
pcm_i2s {
ralink,group = "uartf";
ralink,function = "pcm i2s";
};
};
uartf_gpio_pins: uartf_gpio {
uartf_gpio {
ralink,group = "uartf";
ralink,function = "gpio uartf";
};
};

以下是需要在MT7620a.dts修改的地方，MT7620a.dts中include了mt7620a.dtsi，因为要使能uartf，console如果仍然使用uartlite，需要修改

chosen {
bootargs = "console=ttyS1,57600";
};

在 palmbus@10000000 {中添加uart enable

uart@500 {
status = "okay";
};

在pinctrl {中配置uartf复用的功能

pinctrl {
state_default: pinctrl0 {
gpio {
ralink,group = "i2c";
ralink,function = "gpio";
};
uartf_gpio {
ralink,group = "uartf";
ralink,function = "gpio uartf";
};
};
};

完整的MT7620a.dts内容如下：

/dts-v1/;
/include/ "mt7620a.dtsi"
/ {
compatible = "ralink,mt7620a-eval-board", "ralink,mt7620a-soc";
model = "Ralink MT7620a + MT7610e evaluation board";
chosen {
bootargs = "console=ttyS1,57600";
};
palmbus@10000000 {
spi@b00 {
status = "okay";
m25p80@0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "en25q64";
reg = <0 0>;
linux,modalias = "m25p80", "en25q64";
spi-max-frequency = <10000000>;
partition@0 {
label = "u-boot";
reg = <0x0 0x30000>;
read-only;
};
partition@30000 {
label = "u-boot-env";
reg = <0x30000 0x10000>;
read-only;
};

factory: partition@40000 {
label = "factory";
reg = <0x40000 0x10000>;
read-only;
};
partition@50000 {
label = "firmware";
reg = <0x50000 0x1fb0000>;
};
};
};
uart@500 {
status = "okay";
};
};
pinctrl {
state_default: pinctrl0 {
gpio {
ralink,group = "i2c";
ralink,function = "gpio";
};
uartf_gpio {
ralink,group = "uartf";
ralink,function = "gpio uartf";
};
};
};
ethernet@10100000 {
status = "okay";
mtd-mac-address = <&factory 0x4>;
pinctrl-names = "default";
pinctrl-0 = <&rgmii1_pins &rgmii2_pins &mdio_pins>;
ralink,port-map = "llllw";
//              port@4 {
//                      status = "okay";
//                      phy-mode = "rgmii";
//                      phy-handle = <&phy4>;
//              };
//              port@5 {
//                      status = "okay";
//                      phy-mode = "rgmii";
//                      phy-handle = <&phy5>;
//              };
//              mdio-bus {
//                      status = "okay";
//
//                      phy4: ethernet-phy@4 {
//                              reg = <4>;
//                              phy-mode = "rgmii";
//                      };
//
//                      phy5: ethernet-phy@5 {
//                              reg = <5>;
//                              phy-mode = "rgmii";
//                      };
//              };
};
wmac@10180000 {
ralink,mtd-eeprom = <&factory 0>;
};
gsw@10110000 {
ralink,port4 = "gmac";
};
sdhci@10130000 {
status = "okay";
};
pcie@10140000 {
status = "okay";
};
gpio-keys-polled {
compatible = "gpio-keys";
#address-cells = <1>;
#size-cells = <0>;
poll-interval = <20>;
s2 {
label = "S2";
gpios = <&gpio0 1 1>;
linux,code = <0x100>;
};
s3 {
label = "S3";
gpios = <&gpio0 2 1>;
linux,code = <0x101>;
};
};
ehci@101c0000 {
status = "okay";
};
ohci@101c1000 {
status = "okay";
};
};