2012-12-24 21:16 TI关于da8xx启动内核失败的网页

本文解答了在使用U-Boot加载新的Linux内核过程中遇到的无输出问题，包括内核未写入串口、内核解压后无输出及如何不重新编译内核启用调试输出等，并提供了关于机器编号不匹配导致的问题解决方案。

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No kernel output after U-Boot load

Q: I compiled (new) kernel and started it by (new) U-Boot on a (new) board and I get nooutput after U-Boot copied the kernel to RAM and jumped to it:

## Booting image at 83000000 ...
   Image Name:   Linux-2.6.23-rc3-davinci1
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1434276 Bytes =  1.4 MB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
OK

Starting kernel ...

<nothing, no output>

A: The kernel uncompression code is probably not writing to your serial port. Edit arch/arm/mach-davinci/include/mach/uncompress.h to refer to your UART instead of UART2 (the default).

No output after uncompressing kernel

Q: I get past the kernel uncompressing part but I still get nooutput after that:

## Booting image at 83000000 ...
   Image Name:   Linux-2.6.23-rc3-davinci1
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1434276 Bytes =  1.4 MB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
OK

Starting kernel ...

Uncompressing
Linux.............................................................
................................. done, booting the kernel.

<nothing, no output>

A: Enable

Kernel hacking -> Kernel debugging -> Kernel low-level debugging functions

in Kernel configuration. Drop a printascii() in printk()and see where it hangs.

Enable debug output without kernel recompile

Q: I want to enable kernel debugging, but I don't want (I'm not able) to recompile the kernel. Is there an other way to enable kernel low level debugging output?

A: Instead of above Kernel hacking -> Kernel debugging -> Kernel low-level debugging functionsyou can try to reconfigure serial console at kernel command line. If you use e.g. U-Boot to pass kernel parameters, you can try to replace

... console=/dev/ttyS0,115200n8 ...

with

... console=uart,io,0xe1020000,115200n8 ...

Note: Once the kernel boots fine, you must change the console definition back to the standard value, otherwise the kernel will have a conflict when reserving the memory location again for the ttyS0.

Error a

Q: I enabled low-level debugging function like described above and then get

Linux.............................................................
................................. done, booting the kernel.

Error a

A: "a" stands for "architecture". This means that U-Boot passes the wrong architecture machine number in processor register r1 to kernel. U-Boot and Kernel machine numbers don't match. For possible solutions see below.

Wrong machine number I

Q: My (old/new) U-Boot doesn't start my (new/old) Linux kernel correctly, because the machine numberpassed by U-Boot to the kernel don't match kernels one.

A: Correct your U-Boot and/or Linux kernel to use matching machine numbers.

Wrong machine number II

Q: My (old/new) U-Boot doesn't start my (new/old) Linux kernel correctly, because the machine numbers don't match. I don't want to correct machine numbers. What else can I do?

A: Try hackishpatchto disable machine number in kernel.

Machine numbers

Q: What are these machine numbers this FAQ talks about above?

A: See Machine numbersand machine number registry. Machine number is compiled into U-Boot and passed by register to Linux kernel. Linux kernel has machine number compiled in as well. Both machine numbers have to match, else kernel won't boot.