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.
Showing posts with label u-boot. Show all posts
Showing posts with label u-boot. Show all posts
Sunday, March 07, 2010
Thursday, March 04, 2010
u-boot again
I am still working the u-boot project. After I got the ARM realview ice debugger, my life is easier, but still tough. I traced the assembly code of Linux kernel and compare the execution of the same kernel booted by both boot2 and u-boot. As the boot2 can successfully boot the kernel image, I just need to make sure u-boot can get to the same state that u-boot created for the kernel.
I figured out the memory starting address configuration is not set to proper value in u-boot today, but checking the kernel parameters. However, after I modified the u-boot code, I still can't get through the same point in kernel image. Anyway, there is a problem to be fixed. I'd keep working on that tomorrow, by checking the memory set by boot2/uboot, before the kernel booted.
The Linux kernel needs some settings in ATAG. Those settings will be read by kernel during the boot stage. There are several ATAG parameters, like the memory starting address, size, command line, arch id, etc.
I figured out the memory starting address configuration is not set to proper value in u-boot today, but checking the kernel parameters. However, after I modified the u-boot code, I still can't get through the same point in kernel image. Anyway, there is a problem to be fixed. I'd keep working on that tomorrow, by checking the memory set by boot2/uboot, before the kernel booted.
The Linux kernel needs some settings in ATAG. Those settings will be read by kernel during the boot stage. There are several ATAG parameters, like the memory starting address, size, command line, arch id, etc.
Wednesday, February 24, 2010
u-boot
I have been working on u-boot since last week. I need to port u-boot to our bcmring platform.
We have some example from another team of Broadcom to support u-boot on the 2153 platform, which has a similar ARM core with our bcmring platform.
I got the u-boot to build last week. Since this week, I learned to use JTAG to load the u-boot elf file into the memory of the platform after ddr initialization. I ported the UART driver and then the timer driver. Yesterday, I was able to boot to u-boot shell with JTAG. That's a good milestone.
Today, I studied our 1st boot loader (boot1) and the relation between the boot1 and boot2, the second stage boot loader. As I was trying to replace boot2 with u-boot, after I figured out the memory map of boot2, with the help of Darwin, I managed to load u-boot from boot1 and boot to u-boot shell without using JTAG. That's a big success. I can then work on the nand driver to get u-boot to boot our kernel.
The ethernet driver, sd/mmc support will be followed after the nand driver.
We have some example from another team of Broadcom to support u-boot on the 2153 platform, which has a similar ARM core with our bcmring platform.
I got the u-boot to build last week. Since this week, I learned to use JTAG to load the u-boot elf file into the memory of the platform after ddr initialization. I ported the UART driver and then the timer driver. Yesterday, I was able to boot to u-boot shell with JTAG. That's a good milestone.
Today, I studied our 1st boot loader (boot1) and the relation between the boot1 and boot2, the second stage boot loader. As I was trying to replace boot2 with u-boot, after I figured out the memory map of boot2, with the help of Darwin, I managed to load u-boot from boot1 and boot to u-boot shell without using JTAG. That's a big success. I can then work on the nand driver to get u-boot to boot our kernel.
The ethernet driver, sd/mmc support will be followed after the nand driver.
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