[coreboot] Crazy Intel graphics mtrr

joe at settoplinux.org joe at settoplinux.org
Thu Apr 17 06:21:10 CEST 2008


>On Wed, Apr 16, 2008 at 5:03 PM,  <joe at settoplinux.org> wrote:
>> Hello,
>>  I am noticing some X problems (slow, crashes once and a while) on the RCA 
>RM4100. I think this is related to the crazy way coreboot setup the mtrr. For 
>some reason when the Intel onboard graphics are enabled, coreboot sets up this 
>crazy looking mtrr. I don't think they should all be write-back? Isn't 
>write-combining faster for graphics? Does it need to have a uncachable area?
>>
>
>that is normal.
>
>>  reg00: base=0x00000000 (   0MB), size=  64MB: write-back, count=1
>>  reg01: base=0x04000000 (  64MB), size=  32MB: write-back, count=1
>>  reg02: base=0x06000000 (  96MB), size=  16MB: write-back, count=1
>>  reg03: base=0x07000000 ( 112MB), size=   8MB: write-back, count=1
>==
>>  reg00: base=0x07800000 ( 120MB), size=   8MB: uncachable, count=1
>>  reg01: base=0x00000000 (   0MB), size= 128MB: write-back, count=1
>
>and old kernel like previous one
>64+32+16+8 == (128 - 8)
>
>YH
>
Hmm, so it all adds up but, what is the need for 3 different mtrr's instead of one? Also, what about this:

>> I don't think they should all be write-back? Isn't 
>> write-combining faster for graphics? Does it need to have a uncachable area?

-- 
Thanks,
Joseph Smith
Set-Top-Linux
www.settoplinux.org




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