[coreboot] Out of MTRRs

[Jay Talbott]

I'm working on a coreboot solution for a SkyLake based board that uses
SO-DIMMs.

 

The plan is for two 8GB DIMMs, for a total of 16GB of RAM.

 

But with two 8GB DIMMs installed, I get the following during the boot:

 

Taking a reserved OS MTRR.

Taking a reserved OS MTRR.

Taking a reserved OS MTRR.

ERROR: Not enough MTRRs available! MTRR indexis 10 with 10 MTTRs in total.

Not enough MTRRs: 11 vs 10

Unable to insert temporary MTRR range: 0x00000000ff800000 -
0x0000000100000000 size 0x00800000 type 5

 

This is obviously a problem.

 

If I remove one DIMM, then I just get:

 

Taking a reserved OS MTRR.

Taking a reserved OS MTRR.

 

Still an issue, although at least we don't run out of MTRRs.

 

If I use a single 4GB DIMM instead of an 8GB DIMM, there's no issue with the
MTRR config at all.

 

I'm assuming that I'm not the first person to run into this when using
coreboot on systems with larger amounts of RAM, so I figured I'd ask the
community what's the fix to getting this to work correctly with 16GB of RAM
before trying to figure it out myself.

 

Any help would be most appreciated.

 

Thanks,

 

- Jay

 

Jay Talbott
Principal Consulting Engineer
SysPro Consulting, LLC
3057 E. Muirfield St.
Gilbert, AZ 85298
(480) 704-8045
(480) 445-9895 (FAX)
 <mailto:JayTalbott at sysproconsulting.com> JayTalbott at sysproconsulting.com

 <http://www.sysproconsulting.com/> http://www.sysproconsulting.com

 

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