In cross development, the serial port is usually the most important interface: That is where you can see anything happening! It might be worthwhile to make sure you get serial porting work before you even start playing with Linux. You can find the sample code or gzipped tar ball of a stand-alone program that can do printf. Such a program can even be useful in later debugging staging, e.g., printing out hardware register values.
Before you rush to type 'make', check and modify the following configurations:
- The sample code assumes R4K style CP0 structure. It should apply to most CPUs named above number 4000 and the recent MIPS32/MIPS64.
- Check if you have 1MB RAM size. (You really should have at 1MB to run Linux at all.) It is recommanded you have 8MB RAM or more.
- Is your serial port a standard UART type? If yes, modify the serial code and parameters. If not, you will have to supply your own functions to utilize the UART.
- What is your cross-tool name and path? Modify the Makefile accordingly.
Now, fire your "make" command.
Download the barebone image to your target and give it a run! Connect the serial port to your host machine. Start minicom and hopefully you can see the "Hello, world!" message.
- Make sure your bootloader downloads the image to uncached KSEG1 segment. If your bootloader downloads to the cached KSEG0 area, you will want to run the image from the KSEG0 area too.
- If your bootloader has already initialized the serial port, you may want to skip your own initialization.
- Did you set up minicom correctly? Test it with other machines.
- Hopefully it is not the toolchain problem...
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