[PATCH] ppc32/64: Map prefetchable PCI without guarded bit

Jesse Barnes jbarnes at engr.sgi.com
Fri Mar 25 03:55:54 EST 2005

On Thursday, March 24, 2005 8:54 am, Jesse Barnes wrote:
> On Wednesday, March 23, 2005 10:24 pm, Benjamin Herrenschmidt wrote:
> > While experimenting with framebuffer access performances, we noticed a
> > very significant improvement in write access to it when not setting
> > the "guarded" bit on the MMU mappings. This bit basically says that
> > reads and writes won't have side effects (it allows speculation). It
> > appears that it also disables write combining.
> Doesn't pgprot_writecombine imply non-guarded, so can't you use it instead?
> Either way, you'll probably want to fix fbmem.c as well and turn off

Nevermind about this bit, I just scrolled a little further into your patch :)


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