Yocto开发笔记之《U-boot启动内核流程》（QQ交流群：519230208）
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执行命令
u-boot# env default -f -a; setenv ipaddr 192.168.0.100;setenv serverip 192.168.0.107;setenv image zImage;setenv fdt_file zImage-imx6ul-14x14-evk.dtb;setenv rootfsinfo 'setenv bootargs ${bootargs} root=/dev/nfs ip=dhcp nfsroot=${serverip}:/tftpboot/imx6ulevk.rootfs,v3,tcp';setenv bootcmd_net 'run rootfsinfo; dhcp ${image}; dhcp ${fdt_addr} ${fdt_file}; bootz ${loadaddr} - ${fdt_addr}';setenv bootcmd 'run bootcmd_net'
出现错误
CPU: Freescale i.MX6UL rev1.0 at 396 MHz
CPU: Temperature 38 C
Reset cause: POR
Board: MX6UL 14x14 EVK
I2C: ready
DRAM: 512 MiB
MMC: FSL_SDHC: 0, FSL_SDHC: 1
Display: TFT43AB (480x272)
Video: 480x272x24
In: serial
Out: serial
Err: serial
switch to partitions #0, OK
mmc1 is current device
Net: FEC1
Normal Boot
Hit any key to stop autoboot: 0
BOOTP broadcast 1
DHCP client bound to address 192.168.0.105 (3 ms)
Using FEC1 device
TFTP from server 192.168.0.107; our IP address is 192.168.0.105
Filename 'zImage'.
Load address: 0x80800000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
########################
885.7 KiB/s
done
Bytes transferred = 6070432 (5ca0a0 hex)
BOOTP broadcast 1
DHCP client bound to address 192.168.0.105 (3 ms)
Using FEC1 device
TFTP from server 192.168.0.107; our IP address is 192.168.0.105
Filename 'zImage-imx6ul-14x14-evk.dtb'.
Load address: 0x83000000
Loading: ###
364.3 KiB/s
done
Bytes transferred = 34342 (8626 hex)
Kernel image @ 0x80800000 [ 0x000000 - 0x5ca0a0 ]
Wrong Ramdisk Image Format
Ramdisk image is corrupt or invalid
修改为(Thanks tony)：
U-boot# setenv serverip 192.168.0.107; setenv bootargs console=ttymxc0,115200 debug root=/dev/nfs ip=dhcp nfsroot=${serverip}:/nfsroot/rootfs,v3,tcp dhcp 0x80800000 zImage; dhcp 0x83000000 zImage-imx6ul-14x14-evk.dtb; bootz 0x80800000 - 0x83000000
# 注释
# setenv serverip 192.168.0.107; // 设置服务器地址
# setenv bootargs console=ttymxc0,115200 debug root=/dev/nfs ip=dhcp nfsroot=${serverip}:/nfsroot/rootfs,v3,tcp // boot属性，串口显示log，配置nfs加载rootfs
# dhcp 0x80800000 zImage; // 设置zImage的加载地址
# dhcp 0x83000000 zImage-imx6ul-14x14-evk.dtb; // 设置dtb文件的加载地址
# bootz 0x80800000 - 0x83000000 // 开始加载地址段之间的内容到内存
以下代码可以从tftp加载zImage和zImage-imx6ul-14x14-evk.dtb，但加载rootfs时出错，错误log
cpu cpu0: dev_pm_opp_get_opp_count: device OPP not found (-19) gpio_dvfs: disabling VSD_3V3: disabling can-3v3: disabling regulator-dummy: disabling imx mcc test is registered. snvs_rtc 20cc034.snvs-rtc-lp: setting system clock to 2015-08-19 02:41:11 UTC (1439952071) IP-Config: Failed to open eth0 IP-Config: Failed to open eth1 IP-Config: No network devices available ALSA device list: #0: wm8960-audio VFS: Unable to mount root fs via NFS, trying floppy. VFS: Cannot open root device "nfs" or unknown-block(2,0): error -6 Please append a correct "root=" boot option; here are the available partitions: 1f00 32768 mtdblock0 (driver?) b300 15339520 mmcblk1 driver: mmcblk b301 8192 mmcblk1p1 a9d0174c-01 b302 851968 mmcblk1p2 a9d0174c-02 Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0) random: nonblocking pool is initialized
初步断定是nfs服务器加载失败, 先设置从sd卡中加载rootfs，可以正常启动：
setenv bootargs 'console=ttymxc0,115200 debug ip=dhcp root=/dev/mmcblk1p2 rootwait rw'
进入系统后网卡无法正常打开
root@imx6ulevk:/usr/games# ifconfig eth0 up ifconfig: SIOCSIFFLAGS: No such device
查看系统信息
＃ dmesg | grep eth -C 5
===================================================================================================
常用命令备忘
# env default -f -a // 恢复默认设置 # saveenv // 保存设置到长期存储emmc，否则掉电设置失效 # help or ? // 查看帮助信息 # print // 打印当前环境信息 # setenv ethaddr xx:xx:xx:xx:xx:xx // 因为要上网，如果网卡没有mac地址，随便搞个mac地址
# setenv ethaddr 00.01.02.03.04.05
===================================================================================================
boot四大件儿
Bootloader (U-boot); // 如果没有指定boot设备，默认从SD/MMC启动；
// MFGTool可以把u-boot image烧写到任何所有设备，
// 可以通过dd命令把u-boot image烧写到sdcard
// 通过u-boot命令行可以把u-boot image 烧写到其他设备
Linux kernel image(zImage); // 所有I.MX的板子可以用同一套zImage
A device tree file (.dtb) for the board being used // 适配不同的硬件pin和软件配置文件，专门做适配的一个东东；
// 注意在选择上有个LDO bypass区别，硬件和系统工程师注意
A root file system(rootfs) for the particular system image // busybox, common libraries
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SD卡启动
先准备一张4G卡，如果您有钱用8G也没关系，只不过会有4G浪费不见了，有更多空间需求也可以自己适配。
可以通过一个命令一次烧写四大件儿，XXX.sdcard这个文件都包含了，简单方便。
也可以分批次一个一个烧写四大件儿，灵活。
|
Table 1. Image layout |
|||
|
Start address (sectors) |
Size (sectors) |
Format |
Description |
|
0x400 bytes (2) |
0x9FFC00 bytes (20478) |
RAW |
U-Boot and reserved area |
|
0xa00000 bytes (20480) |
500 Mbytes (1024000) |
FAT |
Kernel zImage and DTBs |
|
0x25800000 bytes (1228800) |
Remaining space |
Ext3/Ext4 |
Rootfs |
准备第一次烧写：
$ cat /proc/partitions // 找到自己sd卡的盘符，别找错了，不然可能毁掉你的操作系统
$ sudo dd if=<.sdcard image> of=/dev/sdx bs=1M conv=fsync // 替换到属于你的.sdcard image和u盘盘符
.sdcard image 这个东西很牛逼，已经对sdcard分好了区，如果你想分开烧写四大件，你就得自己分区了：
$ sudo umount /dev/sdx // 先卸掉设备
$ sudo fdisk /dev/sdx // 进入磁盘分区程序，别怕费事儿，按顺序把下边儿命令敲了吧
p [lists the current partitions] d [to delete existing partitions. Repeat this until no unnecessary partitions
are reported by the 'p' command to start fresh.]
u [switch the unit to sectors instead of cylinders] n [create a new partition] p [create a primary partition - use for both partitions] 1 [the first partition] 20480 [starting at offset sector] 1024000 [size for the first partition to be used for the boot images] p [to check the partitions]
n p 2 1228800 [starting at offset sector, which leaves enough space for the kernel,
the bootloader and its configuration data] <enter> [using the default value will create a partition that extends to
the last sector of the media] p [to check the partitions]
w [this writes the partition table to the media and fdisk exits]
拷贝四大件儿
内容太多，就不一一拷贝了，参考文档《i.MX_Linux_User's_Guide.pdf》
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从NFS启动系统
setenv serverip 192.168.0.107 setenv consoleinfo 'console=ttymxc0,115200' setenv displayinfo 'video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24' setenv loadaddr 0x80800000 setenv fdt_addr 0x83000000 setenv fdt_file 'zImage-imx6ul-14x14-evk.dtb' setenv special 'uart_from_osc' setenv rootfsinfo 'root=/dev/nfs ip=dhcp nfsroot=${serverip}:/nfsroot/rootfs,v3,tcp' setenv bootargsset 'setenv bootargs ${consoleinfo} ${rootfsinfo} ${displayinfo} ${special}' setenv bootcmd_net 'run rootfsinfo bootargsset; dhcp ${image}; dhcp ${fdt_addr} ${fdt_file}; bootz ${loadaddr} - ${fdt_addr}' setenv bootcmd 'run bootcmd_net' －－－－－－－－－－－－－－－－－－－－－－－－－ setenv ipaddr 192.168.2.xxx setenv serverip 192.168.2.xxx setenv bootfile uImage setenv nfsroot /home/carmili/ltib/rootfs setenv bootargs_base 'setenv bootargs console=ttymxc0,115200' setenv bootargs_nfs 'setenv bootargs ${bootargs} root=/dev/nfs rw ip=${ipaddr }{serverip }:192.168.2.1:255.255.255.0::eth0ff nfsroot=${serverip}{nfsroot},v3,tcp setenv bootcmd_net 'run bootargs_base bootargs_nfs;bootm' setenv bootcmd 'tftpboot uImage; run bootcmd_net' －－－－－－－－－－－－－－－－－－－－－－－－－ U-Boot > setenv ipaddr 192.168.0.100 U-Boot > setenv serverip 192.168.0.107 U-Boot > setenv image zImage U-Boot > setenv fdt_file zImage-imx6ul-14x14-evk.dtb U-Boot > setenv rootfsinfo 'setenv bootargs ${bootargs} root=/dev/nfs ip=dhcp nfsroot=${serverip}:/tftpboot/imx6ulevk.rootfs,v3,tcp' U-Boot > setenv bootcmd_net 'run rootfsinfo; dhcp ${image}; dhcp ${fdt_addr} ${fdt_file}; bootz ${loadaddr} - ${fdt_addr}' U-Boot > setenv bootcmd 'run bootcmd_net'
从SD卡启动
U-Boot > setenv mmcpart 1 U-Boot > setenv loadfdt 'fatload mmc ${mmcdev}:${mmcpart} ${fdt_addr} ${fdt_file}' U-Boot > setenv loadkernel 'fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} zImage' U-Boot > setenv bootcmd 'mmc dev ${mmcdev}; run loadkernel; run mmcargs; run loadfdt; bootz $ {loadaddr} - ${fdt_addr};'
