T T wrote: > I would like to port linux kernel to a custom board that contains xc2vp4 > (xilinx fpga) which it include powerpc 405 hard core, uartlite, spi > controller, sdram controller. I don't how to start because I am new to > linux os. Any help is welcome.
The best way to learn is to look at the code of a similar board. Directories that will contain interesting code are arch/ppc/platforms arch/ppc/boot/simple arch/ppc/syslib In the platforms directory, look for a board that is similar to one that you are already familiar with and grep the source tree for its config option (see the Kconfig files). Study the code that is covered by the config option. Don't restrict your search to C files; even Makefiles will contain conditional statements on config options. The first place to start in writing new board support is creating a new arch/ppc/platforms/xxx.c file. Study code to see how those routines init the system and setup the ppc_md structure. For ppc, arch/ppc/kernel/head*.S contains assembly startup code for each supported CPU family. It's a good place to start when finding out how a ppc system is initialized. Code in arch/ppc/boot/simple implements a simple boot loader. A zImage file contains the boot loader and a compressed kernel image. If your board has u-boot support (unlikely) then you don't need anything in arch/ppc/boot/simple for your board - u-boot can load plain vmlinux kernel images. Depending on your bootloader, this might be the first thing you need to implement. In arch/ppc/syslib you'll find support for common chips found on ppc boards. Typically platform code hooks up required files from this area. For other devices like serial, i2c, flash etc that are used by more than one CPU architecture, check other (non-ppc specific) parts of the kernel tree. Before writing any new code for a chip, scan appropriate mail archives to find if any patches are already available. Work towards getting the kernel running to the point where it panics due to no root filesystem being found. There will be a lot of work in getting there though. Getting the serial port working is usually one of the first things to do. Don't concern yourself yet with anything that goes into the root filesystem; you can ask for help on that later when you get there. I hope this was helpful. You might also find the following book useful. http://www.oreilly.com/catalog/belinuxsys/ Good luck! -- James Chapman http://www.katalix.com/
