[coreboot] Porting to Asus M4A78-EM

Juhana Helovuo juhe at iki.fi
Sun Dec 5 11:59:32 CET 2010

Myles Watson wrote:
>>>> I don't see any reason not to move that resource into the northbridge
>>>> to avoid that issue.  It's a simple fix.  Is there a good reason for
>>>> having the MMCONF BAR in the APIC cluster?
>>> This is what I was thinking.  Build tested only.
>>> Signed-off-by: Myles Watson <mylesgw at gmail.com>
>> Oh, this was very good! Thank you! Now I can load Linux kernel on the
>> M4A78-EM, although it doesn't boot successfully yet.
> I'm glad it's getting better.  Your e820 doesn't look right, though.
> [    0.000000] BIOS-provided physical RAM map:
> [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
> [    0.000000]  BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
> [    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
> [    0.000000]  BIOS-e820: 0000000000100000 - 000000002ffef000 (usable)
> [    0.000000]  BIOS-e820: 000000002ffef000 - 0000000040000000 (reserved)
> [    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
> Your devices have resources mapped from c0000000-e0000000 that don't show
> up.  I can't remember where it would get that value from, but I think it is
> worth looking into.

Yes, now I have the board booting to Linux.

And you are right, the PCI resources do not show up. The resources of 
the PCI root device include

PCI: 00:18.0 resource base c0000000 size 10000000 align 28 gran 20 limit 
PCI: 00:18.0 resource base d0000000 size 4400000 align 26 gran 20 limit 

These resources do not show up in the coreboot table either:

coreboot memory table:
  0. 0000000000000000-0000000000000fff: CONFIGURATION TABLES
  1. 0000000000001000-000000000009ffff: RAM
  2. 00000000000c0000-000000002ffeffff: RAM
  3. 000000002fff0000-000000002fffffff: CONFIGURATION TABLES
  4. 0000000030000000-000000003fffffff: RESERVED
  5. 00000000e0000000-00000000efffffff: RESERVED
Wrote coreboot table at: 2fffe000 - 2fffe1bc  checksum ba50

But does it really matter? There is now physical RAM only up to 
40000000. Or is it going to be a problem if there is more than 3 GB RAM?

Best regards,
Juhana Helovuo

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