在调试MPC 8308 过程中，在u-boot下通过tftp将uImage文件下载到内存，
然后通过bootm命令启动内核，会挂死在
Uncompressing Kernel Image ... OK处，在bootm中添加打印发现
死在unlock_ram_in_cache，查看汇编实现没有找到原因。
U-Boot 2009.11-rc1 (Feb 06 2018 - 17:38:45) MPC83XX
Reset Status: Software Hard, External/Internal Soft, External/Internal Hard
CPU: e300c3, MPC8308, Rev: 1.1 at 400 MHz, CSB: 133.333 MHz
Board: Freescale MPC8308ERDB Rev <unknown>
I2C: ready
DRAM: init_func_ram
128 MB
Now running in RAM - U-Boot at: 07f9a000
FLASH: 32 MB
*** Warning - bad CRC, using default environment
PCIE0: link
In: serial
Out: serial
Err: serial
MMC: FSL_ESDHC: 0
Net: eTSEC0, eTSEC1
=> setenv ipaddr 192.168.9.100
=> setenv serverip 192.168.9.135
=> tftp 2000000
Speed: 100, full duplex
Using eTSEC0 device
TFTP from server 192.168.9.135; our IP address is 192.168.9.100
Filename 'uImage'.
Load address: 0x2000000
Loading: #################################################################
##################################################
done
Bytes transferred = 1681275 (19a77b hex)
=> bootm 2000000
## Booting kernel from Legacy Image at 02000000 ...
Image Name: Linux-2.6.29.6-rt23
Created: 2018-02-07 1:06:55 UTC
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 1681211 Bytes = 1.6 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
kernel data at 0x02000040, len = 0x0019a73b (1681211)
Uncompressing Kernel Image ... OK
kernel loaded at 0x00000000, end = 0x00377930
