第二十一期 U-Boot启动OpenWrt实验 《路由器就是开发板》

这一期我们来做一个引导OpenWrt的实验，虽然还没有讲到OpenWrt的内容，但这里我们先拿一个我编译好的固件来实验一下，具体固件怎么编译下一期再讲。

如果使用RalinkSDK3.6的U-Boot进行编译出来的U-Boot启动时TTL会输出如下信息：

3: System Boot system code via Flash.

## Booting image at bf050000 ...

这个地址是Ralin默认的firmware地址。这里我们来分析一下flash的分区结构：

上面这张图一目了然，但是OpenWrt给hg255的的flash分区却和Ralink的分区不一样，我们看一下OpenWrt对hg255d的dts文件：

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";};};};cfi@1f000000 {compatible = "cfi-flash";reg = <0x1f000000 0x1000000>;bank-width = <2>;device-width = <2>;#address-cells = <1>;#size-cells = <1>;partition@0 {label = "u-boot";reg = <0x0 0x40000>;read-only;};partition@30000 {label = "u-boot-env";reg = <0x40000 0x20000>;read-only;};factory: partition@60000 {label = "factory";reg = <0x60000 0x20000>;read-only;};partition@80000 {label = "firmware";reg = <0x80000 0xf60000>;};partition@fa0000 {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>;};};ethernet@10100000 {mtd-mac-address = <&factory 0x28>;};esw@10110000 {ralink,portmap = <0x2f>;};wmac@10180000 {ralink,mtd-eeprom = <&factory 0>;};otg@101c0000 {status = "okay";};};

我把这个文件描述的flash分区画了张图：

可以看出OpenWrt内核的引导地址为0xBF080000，而Ralink的默认引导地址为0xBF050000，如果不修改是无法引导OpenWrt的。这里的解决方案是修改U-Boot目录下 include/config/rt2880.h 的定义文件 的293行

#################################define CFG_BOOTLOADER_SIZE0x30000#define CFG_CONFIG_SIZE0x10000#define CFG_FACTORY_SIZE0x10000#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))###########################################修改为：#define CFG_BOOTLOADER_SIZE0x40000#define CFG_CONFIG_SIZE0x20000#define CFG_FACTORY_SIZE0x20000###########################################

这样就和OpenWrt的flash分区同步了，用前面提到的方法将OpenWrt刷入flash 0xBF080000开始的地址，然后用U-Boot默认方式启动就能看到OpenWrt已经启动了：

启动后telnet可以访问OpenWrt

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SDK下载地址：   https://github.com/aggresss/RFDemo