https://blog.csdn.net/aggresss/article/details/52752388

這一期我們來做一個引導OpenWrt的實驗，雖然還沒有講到OpenWrt的內容，但這裡我們先拿一個我編譯好的韌體來實驗一下，具體韌體怎麼編譯下一期再講。
如果使用RalinkSDK3.6的U-Boot進行編譯出來的U-Boot啟動時TTL會輸出如下資訊：
3: System Boot system code via Flash.
## Booting image at bf050000 ...
這個地址是Ralin預設的firmware地址。這裡我們來分析一下flash的分割槽結構：

上面這張圖一目瞭然，但是OpenWrt給hg255的的flash分割槽卻和Ralink的分割槽不一樣，我們看一下OpenWrt對hg255d的dts檔案：
 

target/linux/ramips/dts/HG255D.dts
######################################
/dts-v1/;
 
/include/ "rt3050.dtsi"
 
/ {
	compatible = "HG255D", "ralink,rt3052-soc";
	model = "HuaWei HG255D";
 
	pinctrl {
		state_default: pinctrl0 {
			gpio {
				ralink,group = "spi", "i2c", "jtag", "rgmii", "mdio", "uartf";
				ralink,function = "gpio";
			};
		};
	};
 
	
 
[email protected] {
		compatible = "cfi-flash";
		reg = <0x1f000000 0x1000000>;
 
		bank-width = <2>;
		device-width = <2>;
		#address-cells = <1>;
		#size-cells = <1>;
 
		[email protected] {
			label = "u-boot";
			reg = <0x0 0x40000>;
			read-only;
		};
 
		[email protected]
 
 {
			label = "u-boot-env";
			reg = <0x40000 0x20000>;
			read-only;
		};
 
		factory: [email protected] {
			label = "factory";
			reg = <0x60000 0x20000>;
			read-only;
		};
 
		[email protected] {
			label = "firmware";
			reg = <0x80000 0xf60000>;
		};
 
		[email protected] {
			label = "factory-orig";
			reg = <0xfa0000 0x20000>;
			read-only;
		};
	};
 
	gpio-leds {
		compatible = "gpio-leds";
		power {
			label = "hg255d:power";
			gpios = <&gpio0 8 1>;
		};
		internet {
			label = "hg255d:internet";
			gpios = <&gpio0 13 1>;
		};
		wifi {
			label = "hg255d:wlan";
			gpios = <&gpio0 14 1>;
		};
		usb {
			label = "hg255d:usb";
			gpios = <&gpio0 9 1>;
		};
		wps {
			label = "hg255d:wps";
			gpios = <&gpio0 12 1>;
		};
		voice {
			label = "hg255d:voice";
			gpios = <&gpio0 5 1>;
		};
	};
 
	gpio-keys-polled {
		compatible = "gpio-keys-polled";
		#address-cells = <1>;
		#size-cells = <0>;
		poll-interval = <10>;
		reset {
			label = "reset";
			gpios = <&gpio0 4 1>;
			linux,code = <0x198>;
		};
		wps {
			label = "wps";
			gpios = <&gpio0 10 1>;
			linux,code = <0x211>;
		};
		rfkill {
			label = "rfkill";
			gpios = <&gpio0 0 1>;
			linux,code = <0xf7>;
		};
	};
 
	[email protected] {
		mtd-mac-address = <&factory 0x28>;
	};
 
	[email protected] {
		ralink,portmap = <0x2f>;
	};
 
	[email protected] {
		ralink,mtd-eeprom = <&factory 0>;
	};
 
	[email protected] {
		status = "okay";
	};
};

我把這個檔案描述的flash分割槽畫了張圖：

可以看出OpenWrt核心的引導地址為0xBF080000，而Ralink的預設引導地址為0xBF050000，如果不修改是無法引導OpenWrt的。這裡的解決方案是修改U-Boot目錄下 include/config/rt2880.h 的定義檔案 的293行

################################
#define CFG_BOOTLOADER_SIZE	0x30000
#define CFG_CONFIG_SIZE		0x10000
#define CFG_FACTORY_SIZE	0x10000
#define CFG_ENV_ADDR		(CFG_FLASH_BASE + CFG_BOOTLOADER_SIZE)
#define CFG_FACTORY_ADDR	(CFG_FLASH_BASE + CFG_BOOTLOADER_SIZE + CFG_CONFIG_SIZE)
#define CFG_KERN_ADDR		(CFG_FLASH_BASE + (CFG_BOOTLOADER_SIZE + CFG_CONFIG_SIZE + CFG_FACTORY_SIZE))
###########################################
修改為：
#define CFG_BOOTLOADER_SIZE	0x40000
#define CFG_CONFIG_SIZE		0x20000
#define CFG_FACTORY_SIZE	0x20000
###########################################

這樣就和OpenWrt的flash分割槽同步了，用前面提到的方法將OpenWrt刷入flash 0xBF080000開始的地址，然後用U-Boot預設方式啟動就能看到OpenWrt已經啟動了：

啟動後telnet可以訪問OpenWrt

----------------------------------

SDK下載地址：   https://github.com/aggresss/RFDemo