OpenWRT版本：17
一、DTS
DTS是Device Tree Source的缩写，它用来描述设备的硬件细节。说简单点就是开发板的配置文件。
二、分析OpenWRT的dts文件
以rt5350.dtsi作为分析
//DTS格式有点类似Json
/ { // "/"表示root节点
//#address-cells和#size-cells分别决定reg属性的address和length字段的长度。比如reg<0x500 0x100>,0x500和0x100两个数值都是32位的
#address-cells = <1>; //地址长度为1个32位的整型
#size-cells = <1>; //length为1个32位的整型
//ralink:厂商 rt5350-soc:具体的芯片型号
compatible = "ralink,rt5350-soc"; //定义系统名称，compatible属性用于驱动和设备的绑定，属性值形式：<manufacturer>,<model>
cpus { //芯片中的所有cpu定义
cpu@0 { //cpu@0表示第一个cpu,如果还有其他cpu就依次定义为cpu@1 cpu@2 .....
compatible = "mips,mips24KEc"; //mips的cpu内核，mips24KEc是具体型号
};
};
chosen {
bootargs = "console=ttyS0,57600"; //启动参数，定义了串口ttyS0为调试串口，波特率为57600
};
cpuintc: cpuintc@0 {
#address-cells = <0>;
#interrupt-cells = <1>; //中断号长度
interrupt-controller;
compatible = "mti,cpu-interrupt-controller";
};
aliases { //定义别名
spi0 = &spi0;
spi1 = &spi1;
serial0 = &uartlite; //uartlite的别名为serial0
};
palmbus@10000000 { // @后面代表address
compatible = "palmbus";
reg = <0x10000000 0x200000>; //address: 0x10000000 length:0x200000
ranges = <0x0 0x10000000 0x1FFFFF>; //地址转换表 ：<子地址 父地址 子地址空间的映射大小>
#address-cells = <1>; //决定子节点reg的address字段长度
#size-cells = <1>; //决定子节点reg的length字段长度
sysc@0 {
compatible = "ralink,rt5350-sysc", "ralink,rt3050-sysc"; //兼容rt5350和rt3050
reg = <0x0 0x100>;
};
timer@100 {
compatible = "ralink,rt5350-timer", "ralink,rt2880-timer";
reg = <0x100 0x20>;
//在RT5350中，将GPIO设置为中断方式，当它触发中断时，CPU的中断控制器先获取中断，在这里叫一级中断。
//判断它是GPIO中断，然后进入GPIO中断控制器判断是哪个GPIO产生的中断，这里叫二级中断，再进行中断处理。
interrupt-parent = <&intc>; //当上级发生intc中断时才来查询是否是该中断。
interrupts = <1>; //中断等级
};
watchdog@120 {
compatible = "ralink,rt5350-wdt", "ralink,rt2880-wdt";
reg = <0x120 0x10>;
resets = <&rstctrl 8>;
reset-names = "wdt";
interrupt-parent = <&intc>;
interrupts = <1>;
};
intc: intc@200 {
compatible = "ralink,rt5350-intc", "ralink,rt2880-intc";
reg = <0x200 0x100>;
resets = <&rstctrl 19>;
reset-names = "intc";
interrupt-controller;
#interrupt-cells = <1>;
interrupt-parent = <&cpuintc>;
interrupts = <2>;
};
memc@300 {
compatible = "ralink,rt5350-memc", "ralink,rt3050-memc";
reg = <0x300 0x100>;
resets = <&rstctrl 20>;
reset-names = "mc";
interrupt-parent = <&intc>;
interrupts = <3>;
};
uart@500 {
compatible = "ralink,rt5350-uart", "ralink,rt2880-uart", "ns16550a";
reg = <0x500 0x100>;
resets = <&rstctrl 12>;
reset-names = "uart";
interrupt-parent = <&intc>;
interrupts = <5>;
reg-shift = <2>;
status = "disabled";
};
gpio0: gpio@600 {
compatible = "ralink,rt5350-gpio", "ralink,rt2880-gpio";
reg = <0x600 0x34>;
resets = <&rstctrl 13>;
reset-names = "pio";
interrupt-parent = <&intc>;
interrupts = <6>;
gpio-controller;
#gpio-cells = <2>;
ralink,gpio-base = <0>;
ralink,num-gpios = <22>;
ralink,register-map = [ 00 04 08 0c
20 24 28 2c
30 34 ];
};
gpio1: gpio@660 {
compatible = "ralink,rt5350-gpio", "ralink,rt2880-gpio";
reg = <0x660 0x24>;
interrupt-parent = <&intc>;
interrupts = <6>;
gpio-controller;
#gpio-cells = <2>;
ralink,gpio-base = <22>;
ralink,num-gpios = <6>;
ralink,register-map = [ 00 04 08 0c
10 14 18 1c
20 24 ];
status = "disabled"; //本模块状态
};
i2c@900 {
compatible = "link,rt5350-i2c", "ralink,rt2880-i2c";
reg = <0x900 0x100>;
resets = <&rstctrl 16>;
reset-names = "i2c";
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&i2c_pins>;
status = "disabled";
};
spi0: spi@b00 {
compatible = "ralink,rt5350-spi", "ralink,rt2880-spi";
reg = <0xb00 0x40>;
resets = <&rstctrl 18>;
reset-names = "spi";
#address-cells = <1>;
#size-cells = <1>;
pinctrl-names = "default";
pinctrl-0 = <&spi_pins>;
status = "disabled";
};
spi1: spi@b40 {
compatible = "ralink,rt5350-spi", "ralink,rt2880-spi";
reg = <0xb40 0x60>;
resets = <&rstctrl 18>;
reset-names = "spi";
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&spi_cs1>;
status = "disabled";
};
uartlite: uartlite@c00 {
compatible = "ralink,rt5350-uart", "ralink,rt2880-uart", "ns16550a";
reg = <0xc00 0x100>;
resets = <&rstctrl 19>;
reset-names = "uartl";
interrupt-parent = <&intc>;
interrupts = <12>;
pinctrl-names = "default";
pinctrl-0 = <&uartlite_pins>;
reg-shift = <2>;
};
systick@d00 {
compatible = "ralink,rt5350-systick", "ralink,cevt-systick";
reg = <0xd00 0x10>;
interrupt-parent = <&cpuintc>;
interrupts = <7>;
};
};
pinctrl { //引脚控制
compatible = "ralink,rt2880-pinmux";
pinctrl-names = "default";
pinctrl-0 = <&state_default>;
state_default: pinctrl0 {
};
spi_pins: spi {
spi {
ralink,group = "spi";
ralink,function = "spi";
};
};
i2c_pins: i2c {
i2c {
ralink,group = "i2c";
ralink,function = "i2c";
};
};
phy_led_pins: phy_led {
phy_led {
ralink,group = "led";
ralink,function = "led";
};
};
uartlite_pins: uartlite {
uart {
ralink,group = "uartlite";
ralink,function = "uartlite";
};
};
uartf_pins: uartf {
uartf {
ralink,group = "uartf";
ralink,function = "uartf";
};
};
spi_cs1: spi1 {
spi1 {
ralink,group = "spi_cs1";
ralink,function = "spi_cs1";
};
};
};
rstctrl: rstctrl {
compatible = "ralink,rt5350-reset", "ralink,rt2880-reset";
#reset-cells = <1>;
};
usbphy: usbphy {
compatible = "ralink,rt3352-usbphy";
#phy-cells = <1>;
resets = <&rstctrl 22 &rstctrl 25>;
reset-names = "host", "device";
};
ethernet@10100000 {
compatible = "ralink,rt5350-eth";
reg = <0x10100000 0x10000>;
resets = <&rstctrl 21 &rstctrl 23>;
reset-names = "fe", "esw";
interrupt-parent = <&cpuintc>;
interrupts = <5>;
mediatek,switch = <&esw>;
};
esw: esw@10110000 {
compatible = "ralink,rt3050-esw";
reg = <0x10110000 0x8000>;
resets = <&rstctrl 23>;
reset-names = "esw";
interrupt-parent = <&intc>;
interrupts = <17>;
};
wmac@10180000 {
compatible = "ralink,rt5350-wmac", "ralink,rt2880-wmac";
reg = <0x10180000 0x40000>;
interrupt-parent = <&cpuintc>;
interrupts = <6>;
ralink,eeprom = "soc_wmac.eeprom";
};
ehci@101c0000 {
compatible = "generic-ehci";
reg = <0x101c0000 0x1000>;
phys = <&usbphy 1>;
phy-names = "usb";
interrupt-parent = <&intc>;
interrupts = <18>;
};
ohci@101c1000 {
compatible = "generic-ohci";
reg = <0x101c1000 0x1000>;
phys = <&usbphy 1>;
phy-names = "usb";
interrupt-parent = <&intc>;
interrupts = <18>;
};
};
三、OpenWRT串口的使用
以RT5350进行举例：
1、进入openwrt/target/linux/ramips/dts目录，打开rt5350.dtsi,即上面的文件。找到下面的内容：
将红色框框的内容去掉就使能了串口。
2、因为uart的配置在uartlite（调试串口）前面，所以uart会被初始化为ttyS0,而ttyS0之前却被配置为调试串口。
为了解决这个问题，我们将uart的配置放到uartlite后面就可以了！
3、串口引脚之前被配置为普通IO口，所以为了防止干扰需要把IO口中的配置去掉。打开openwrt/target/linux/ramips/dts/MPRA2.dts,找到下面内容
把红色框框的内容去掉。
4、重新编译就OK了！ 将编译好的固件下载到开发板后启动系统后，在/dev/目录下会多出ttyS1这个设备。这个就是我们添加的串口设备。
