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Date: Sun, 2 Nov 2014 17:07:46 +0100
From: Tijl Coosemans <tijl@FreeBSD.org>
To: Nathan Whitehorn <nwhitehorn@freebsd.org>
Subject: Re: svn commit: r273963 - head/sys/dev/agp
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On Sun, 02 Nov 2014 07:27:24 -0800 Nathan Whitehorn <nwhitehorn@freebsd.org> wrote:
> There is actually a write-combining memory type on PowerPC. You can set 
> it the same way as on x86 (with VM_MEMATTR_WRITE_COMBINING).

Yes, that's what the patch does, but in sys/powerpc (aim/mmu_oea.c,
aim/mmu_oea64.c and booke/pmap.c) VM_MEMATTR_WRITE_COMBINING becomes
PTE_I meaning Caching Inhibited.  Does powerpc do write-combining for
this type?

That code also maps VM_MEMATTR_WRITE_BACK to PTE_I by the way.  I think
that should be PTE_M (write-back caching + cache coherency).