On 04/05/11 18:54, Rudolf Marek wrote:
Hello,
I was asked to post it here too.
I would like to announce that I was able to boot Linux using u-boot on AMD64 motherboard Asrock 939A785G. The development was done on QEMU.
Excellent - U-Boot on a new x86 board
How does it work?
Coreboot does the complete HW init including memory setup PCI etc. When finishes it loads u-boot.
This is one of the ways I was thinking of getting U-Boot running on mainstream PC boards. The other is to create U-Boot as a GRUB payload. Either way, it's all about getting the SDRAM initialised
[Snip]
How the porting was done is described here:
http://blogs.coreboot.org/blog/2011/04/30/u-boot-as-coreboot-payload/
Excellent write-up - Thanks!
http://www.coreboot.org/pipermail/coreboot/2011-April/064877.html http://www.coreboot.org/pipermail/coreboot/2011-May/064914.html http://www.coreboot.org/pipermail/coreboot/2011-May/064915.html
And boot log http://assembler.cz/minicom42.txt
This project started "just for fun" or "because I can". Maybe there are some real uses. If you can think of some, please let me know.
Well, that's why I started too - kudos for the effort
Anyone with more free time could work on this?
Well I did have someone else contact me about doing exactly as you have done (I have Bcc'd him in case he is interested)
As the U-Boot x86 maintainer, I am extremely interested in going further with this and am keen to help get your work mainlined
I'm not subscribed, please cc me. I'm ccing coreboot mailing list too.
OK, a few little points which may help answer some questions you didn't realise you even had ;)
- The build warnings and errors you incurred are probably fixed in mainline (x86 is a bit of a forgotten cousin which gets broken when global patches are made to Makefile, linker scripts etc). If you still have problems compiling the latest U-Boot git head, please post them to the mailing list and I'll sort them out ASAP - The x86 port of U-Boot was the first to implement the (now pretty much standard) relocation scheme. Understanding it is a Very Good Idea(tm) - SYS_TEXT_BASE=0×19000000 is very specific to the eNET - It is the start of non-volatile (battery backed) SRAM. We can run from SRAM prior to initialising SDRAM, so I use it as an alternative to Flash for testing new builds (reset -> TFTP new image to 0x19000000 -> go 19000000) - When launching U-Boot as a payload from Coreboot, you really don't need to worry about what is at the end of the image (reset vector and jump to protected mode). All the fun begins at the first byte of u-boot.bin which is the first line of code in start.S - CONFIG_SYS_INIT_SP_ADDR is a temporary stack pointer which is used during the relocation of U-Boot from ROM (Flash) into SDRAM. Typically the CPU's Cache-As-RAM (CAR) capability is used. However, if SDRAM is already initialised, you can set CONFIG_SYS_INIT_SP_ADDR to anywhere in SDRAM that will not get clobbered by the relocation - I'm in the middle of re-writing the entire real-mode switch code and real-mode support in U-Boot. The new code allows you to write real-mode code in C - I even have the Linux real-mode printf ported :) This will make writing your own 'BIOS' code for your board a lot easier - Ultimately, I would like to bypass Linux's real-mode stub (like GRUB) and ditch the real-mode code (for the purpose of booting Linux)
I would really like to see some U-Boot patches on the mailing list - Technically U-Boot is meant to be a stand-alone and self-sufficient, but I think for x86 there is merit in creating board configuration that gets boot-strapped by Coreboot (we just need to make sure the documentation is up-to-scratch)
Looking forward to moving this forward
Regards,
Graeme