[coreboot] Enabling 4MB window in LPC adressing space

llandre r&d2 at dave-tech.it
Mon May 26 12:51:15 CEST 2008

>>>> However it does not work:
>>>> a) white LED on dongle is still off
>>> See http://coreboot.org/viewvc?view=rev&root=coreboot-v3&revision=660
>>> and do it in a similar place
>> Ok, thank you for your suggestion. I'll try it.
> This particular spot enables 4MB mode in mainboard stage1, which I'd
> think would be early enough, as it's right after the enabling of serial
> output (and the 4MB mode LED should be lighting up). Then again, I'd
> think that your previous spot should have been early enough as well, so
> not sure what the issue is.
Also when the post code logger is enabled (jumper 7-8 shorted), we see 
on the USB virtual serial port these strings only: "x00" .
So we suspect dongle is not getting the the I/O write operations at all.
Any idea?

>>>> b) coreboot prints:
>>>> Before VSA:
>> ...
>> option ROM_SIZE=4*1024*1024-36*1024
>> Is this correct?
> Two questions about this:
> 1) Why do you need a 4MB ROM? Do you have linux as a payload or what?
Yes. I need to boot a linux kernel. At the moment I don't see any other 
ways to do that.

> 2) Don't you have VGA ROM added to the ROM? Your ROM_SIZE seems to
> indicate there is no room for that, and the log seems to indicate it's
> trying to do graphics init, which my ignorancy makes me now believe it's
> trying to init the VGA ROM and doesn't find it. Maybe you don't have VGA
> ROM included, but using a VSA that does the VGA init stuff which might
> need a VGA ROM to pass? I'm not sure about these specifics, but I do
> have to use a different VSA on coreboot-v2 and coreboot-v3, with my v2
> code having a VGA ROM too, and v3 not - this might very well be just
> codebase and coreboot VSA init differences, but could also be related to
> VGA - hopefully someone who knows will chime in, I've been wondering
> about the differences in the VSA versions for a while.
I suspect VGA ROM is not found by coreboot because it can't access whole 
4MB window.


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