一、启动分析

uboot启动后会通过检测lx2160ardb_boot.scr配置文件，实现默认启动引导。此系列芯片引导方式一样。

打开./configs/board/lx2160ardb_rev2/manifest文件分析

vim ./configs/board/lx2160ardb_rev2/manifest

distroboot=\
'env exists dtb || setenv dtb fsl-lx2160a-rdb.dtb;'\
'env exists kernel_image || setenv kernel_image Image;'\
'env exists devpart_boot || setenv devpart_boot 2;'\
'env exists devpart_root || setenv devpart_root 4;'\
'part uuid $devtype $devnum:$devpart_root partuuidr;'\
'setenv bootargs console=ttyAMA0,115200 earlycon=pl011,mmio32,0x21c0000 root=PARTUUID=$partuuidr rw rootwait pci=pcie_bus_perf $othbootargs;'\
'load $devtype $devnum:$devpart_boot $kernel_addr_r $kernel_image;'\
'load $devtype $devnum:$devpart_boot $fdt_addr_r $dtb;'\
'env exists secureboot && echo validating secureboot && run secureboot_validate;'\
'booti $kernel_addr_r - $fdt_addr_r'


distroboot_ima=\
'env exists dtb || setenv dtb fsl-lx2160a-rdb.dtb;'\
'env exists kernel_image || setenv kernel_image Image;'\
'env exists devpart_boot || setenv devpart_boot 2;'\
'env exists devpart_root || setenv devpart_root 4;'\
'part uuid $devtype $devnum:$devpart_root partuuidr;'\
'load $devtype $devnum:$devpart_boot $kernel_addr_r $kernel_image;'\
'load $devtype $devnum:$devpart_boot $fdt_addr_r $dtb;'\
'setenv initramfs_addr_r 0xb0000000; setenv initramfsheader_addr_r 0x80300000;'\
'load $devtype $devnum:$devpart_boot $initramfs_addr_r initramfs.img;'\
'env exists secureboot && echo validating secureboot && run secureboot_validate;'\
'setenv bootargs console=ttyAMA0,115200 earlycon=pl011,mmio32,0x21c0000 root=PARTUUID=$partuuidr rw rootwait pci=pcie_bus_perf $othbootargs;'\
'booti $kernel_addr_r $initramfs_addr_r $fdt_addr_r'

通过分析配置文件，发现Linux和rootfs的引导取决于devpart_boot和devpart_root两个变量，所以通过修改这两个变量值，便可动态实现，分区引导切换。

二、手动引导切换

进入uboot命令行

setenv devpart_boot  2
setenv devpart_root  4
saveenv

2和4代表分区号

三、动态引导切换

如实现动态引导切换需要通过fw_env工具实现。请参照《fw-env开启文件系统设置uboot环境变量》http://www.recologypower.com:9080/?p=1247

四、分区处理

flex-installer -i pf -p 6P=200M:1536M:128M:13G:1536M:-1 -d /dev/sdx

五、烧录程序

1、进入uboot修改源码

vim include/configs/lx2160a_common.h

最后增加

/*Begin:add by zhaobaoxing for env*/
#define CONFIG_SYS_MMC_ENV_DEV          0
#define CONFIG_ENV_SIZE                 0x2000          /* 8KB */
#define CONFIG_ENV_SECT_SIZE            0x20000
#define CONFIG_ENV_OFFSET               0x500000
#define CONFIG_ENV_ADDR                 (CONFIG_SYS_FLASH_BASE + CONFIG_ENV_OFFSET)
/*End:add by zhaobaoxing for env*/

2、修改fw_env.config文件

# Configuration file for fw_(printenv/setenv) utility.
# Up to two entries are valid, in this case the redundant
# environment sector is assumed present.
# Notice, that the "Number of sectors" is not required on NOR and SPI-dataflash.
# Futhermore, if the Flash sector size is omitted, this value is assumed to
# be the same as the Environment size, which is valid for NOR and SPI-dataflash
# Device offset must be prefixed with 0x to be parsed as a hexadecimal value.

# NOR example
# MTD device name       Device offset   Env. size       Flash sector size       Number of sectors
#/dev/mtd1              0x0000          0x4000          0x4000
#/dev/mtd2              0x0000          0x4000          0x4000

# MTD SPI-dataflash example
# MTD device name       Device offset   Env. size       Flash sector size       Number of sectors
#/dev/mtd5              0x4200          0x4200
#/dev/mtd6              0x4200          0x4200

# NAND example
#/dev/mtd0              0x4000          0x4000          0x20000                 2

# On a block device a negative offset is treated as a backwards offset from the
# end of the device/partition, rather than a forwards offset from the start.

# Block device example
/dev/mmcblk0            0x500000                0x2000
#/dev/mmcblk0           -0x20000        0x20000

# VFAT example
#/boot/uboot.env        0x0000          0x4000

# UBI volume
#/dev/ubi0_0            0x0             0x1f000         0x1f000
#/dev/ubi0_1            0x0             0x1f000         0x1f000

# UBI volume by name
#/dev/ubi0:env          0x0             0x1f000         0x1f000
#/dev/ubi0:env-redund   0x0             0x1f000         0x1f000
~