[U-Boot] U-boot & x86 & coreboot

[Simon Glass]

Hi Daniel,

On Fri, Jul 19, 2013 at 1:49 AM, Rossier Daniel
<Daniel.Rossier at heig-vd.ch>wrote:

> Hi Simon,
> (My first name is Daniel ;-)
>
> I finally succeeded in booting u-boot on QEMU/x86 and even using tftp with
> networking.
> And thanks for your tips.
> First, I changed my version of qemu (from git back to 1.4.50) which solved
> the problem of eclipse/gdb. Now it works.
>
> Then, using the "pc" machine of QEMU, coreboot defines the CAR address at
> 0x19200000 does not work on the emulated PC:
> when U-boot tries to writes all information required by the GDT, it does
> not write anything at this address: that explains why
> the system crashes on the instruction following the lgdt in setup_gdt
> (loading the GDT with all values at 0 makes any further access including
> code not possible).
>
> So, I changed to 0x01200000 which still remains an accessible portion of
> RAM as configured by coreboot. I got the U-boot banner,
> but still with some crashes. The following bug concerned the use of rdtsc
> instruction which is not supported by QEMU yet.
> So I hardcoded a value like 0xf10 in get_tbclk_mhz() so that no access to
> tsc is necessary (ok, just for an approximation in a first time).
> I was able to the the u-boot> prompt.
>
> I also added CONFIG_E1000 to have the network enabled (e1000 is supported
> by the "pc" machine) in order to use tftp (I want to be able to
> transfer some small piece of x86 code and test it in u-boot). And a new
> problem occurred:
> tftp unconditionally leaded to an "access violation" return by the local
> tftp server of qemu. After some quite long hours of debugging, and comparing
> with old version of U-boot, I found a bug in lib/vsprintf.c. In some case,
> the null-termination character is not set at the right place leading to a
> bad length of string.
> I attached the patch which solved my problem.
>

Sound like a lot of progress!

Could you please send that patch to the mailing list? I did notice it but
have not got around to sending out one.


>
> I'm now able to transfer any file in U-boot/qemu/x86. Great! In a near
> future, I will also enable saveenv in order to preserve the environment in
> a flash file.
>

Sounds great.

Regards,
Simon