I finally get u-boot working on our bcmring platform on Friday. I had the hunch on Thursday that the ATAG parameters were not set properly that kernel can't boot. I used JTAG to examine the memory where the ATAG paramters stored. By comparing the memory content set by the working boot2 loader and the u-boot, I found that the command line for kernel wasn't set at all in u-boot. It turns out to be a configuration error in the configuration header files. By setting the proper command line for kernel, I can finally boot the kernel by using u-boot. That's a big progress and I made the u-boot works in two weeks.
In doing this project, I got more understanding of the kernel booting procedure, the ATAG parameters, and u-boot itself. After discussing with my lead, the upcoming work for u-boot includes:
* deliver the changes into linux-c for u-boot support, with proper parameters and configurations.
* upgrade u-boot to the latest version and get it working on bcmring platform.
* port ethernet driver to u-boot, so that the network boot and network rootfs will be supported.
* if time permits, I may get u-boot or other bootloader working for bcmhana as well.
