openwrt DTSI文件解译

build_dir/target-mipsel_24kec+dsp_uClibc-0.9.33.2/linux-ramips_rt305x/linux-3.10.36/arch/mips/ralink/dts/rt3050.dtsi

/ {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "ralink,rt3050-soc", "ralink,rt3052-soc", "ralink,rt3350-soc";

	cpus {
		cpu@0 {
			compatible = "mips,mips24KEc";
		};
	};

	chosen {
		bootargs = "console=ttyS0,57600";
	};

	cpuintc: cpuintc@0 {
		#address-cells = <0>;
		#interrupt-cells = <1>;
		interrupt-controller;
		compatible = "mti,cpu-interrupt-controller";
	};

	palmbus@10000000 {   //地址
		compatible = "palmbus";
		reg = <0x10000000 0x200000>;
		ranges = <0x0 0x10000000 0x1FFFFF>;

		#address-cells = <1>;
		#size-cells = <1>;

		sysc@0 {
			compatible = "ralink,rt3052-sysc", "ralink,rt3050-sysc";
			reg = <0x0 0x100>;
		};

		timer@100 {
			compatible = "ralink,rt3052-timer", "ralink,rt2880-timer";
			reg = <0x100 0x20>;

			interrupt-parent = <&intc>;
			interrupts = <1>;
		};

		watchdog@120 {
			compatible = "ralink,rt3052-wdt", "ralink,rt2880-wdt";
			reg = <0x120 0x10>;

			resets = <&rstctrl 8>;
			reset-names = "wdt";

			interrupt-parent = <&intc>;
			interrupts = <1>;
		};

		intc: intc@200 {
			compatible = "ralink,rt3052-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,rt3052-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,rt3052-gpio", "ralink,rt2880-gpio";
			reg = <0x600 0x34>;  //从0X600开始映射多少地址

			gpio-controller;
			#gpio-cells = <2>;

			ralink,gpio-base = <0>;
			ralink,num-gpios = <24>;
			ralink,register-map = [ 00 04 08 0c
						20 24 28 2c
						30 34 ];  //各寄存器的地址

			resets = <&rstctrl 13>;
			reset-names = "pio";      //名字为PIO

			interrupt-parent = <&intc>;
			interrupts = <6>;          //中断号为6

			status = "disabled";
		};

		gpio1: gpio@638 {
			compatible = "ralink,rt3052-gpio", "ralink,rt2880-gpio";
			reg = <0x638 0x24>;

			gpio-controller;
			#gpio-cells = <2>;

			ralink,gpio-base = <24>;
			ralink,num-gpios = <16>;
			ralink,register-map = [ 00 04 08 0c
						10 14 18 1c
						20 24 ];

			status = "disabled";
		};

		gpio2: gpio@660 {
			compatible = "ralink,rt3052-gpio", "ralink,rt2880-gpio";
			reg = <0x660 0x24>;

			gpio-controller;
			#gpio-cells = <2>;

			ralink,gpio-base = <40>;
			ralink,num-gpios = <12>;
			ralink,register-map = [ 00 04 08 0c
						10 14 18 1c
						20 24 ];

			status = "disabled";
		};

		spi@b00 {
			compatible = "ralink,rt3050-spi", "ralink,rt2880-spi";
			reg = <0xb00 0x100>;

			resets = <&rstctrl 18>;
			reset-names = "spi";

			#address-cells = <1>;
			#size-cells = <0>;

			status = "disabled";
		};

		uartlite@c00 {
			compatible = "ralink,rt3052-uart", "ralink,rt2880-uart", "ns16550a";
			reg = <0xc00 0x100>;

			resets = <&rstctrl 19>;
			reset-names = "uartl";

			interrupt-parent = <&intc>;
			interrupts = <12>;

			reg-shift = <2>;
		};

	};

	rstctrl: rstctrl {
		compatible = "ralink,rt3050-reset", "ralink,rt2880-reset";
		#reset-cells = <1>;
	};

	ethernet@10100000 {
		compatible = "ralink,rt3050-eth";
		reg = <0x10100000 10000>;

		interrupt-parent = <&cpuintc>;
		interrupts = <5>;

		status = "disabled";
	};

	esw@10110000 {
		compatible = "ralink,rt3050-esw";
		reg = <0x10110000 8000>;

		interrupt-parent = <&intc>;
		interrupts = <17>;

		status = "disabled";
	};

	wmac@10180000 {
		compatible = "ralink,rt3050-wmac", "ralink,rt2880-wmac";
		reg = <0x10180000 40000>;

		interrupt-parent = <&cpuintc>;
		interrupts = <6>;

		status = "disabled";
	};

	usb@101c0000 {
		compatible = "ralink,rt3050-usb", "snps,dwc2";
		reg = <0x101c0000 40000>;

		interrupt-parent = <&intc>;
		interrupts = <18>;

		resets = <&rstctrl 22>;
		reset-names = "otg";

		status = "disabled";
	};
};

Linux在启动后，到C入口时，会执行以下操作，加载系统平台上的总线和设备：

start_kernel() --> setup_arch() --> unflatten_device_tree() 

unflatten_device_tree()的代码如下：

 void __init unflatten_device_tree(void)
 {
     __unflatten_device_tree(initial_boot_params, &allnodes,
                 early_init_dt_alloc_memory_arch);

     /* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
     of_alias_scan(early_init_dt_alloc_memory_arch);
 }

 在执行完unflatten_device_tree()后，DTS节点信息被解析出来，保存到allnodes链表中，allnodes会在后面被用到。

随后，当系统启动到board文件时，会调用.init_machine，高通8974平台对应的是msm8974_init()。接着调用of_platform_populate(....)接口，加载平台总线和平台设备。至此，系统平台上的所有已配置的总线和设备将被注册到系统中。注意：不是dtsi文件中所有的节点都会被注册，在注册总线和设备时，会对dts节点的状态作一个判断，如果节点里面的status属性没有被定义，或者status属性被定义了并且值被设为“ok”或者“okay”，其他情况则不被注册到系统中。