Messages in this thread | | | Date | Wed, 22 Apr 2015 17:33:48 +0200 | From | "Luis R. Rodriguez" <> | Subject | Re: [PATCH v4 2/2] IB/qib: use arch_phys_wc_add() |
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On Wed, Apr 22, 2015 at 09:54:38AM -0400, Doug Ledford wrote: > On Tue, 2015-04-21 at 14:50 -0700, Luis R. Rodriguez wrote: > > This: > > + /* MTRR was used if this is non-zero */ > > + if (!dd->wc_cookie) > > vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); > > And this: > > + dd->wc_cookie = arch_phys_wc_add(pioaddr, piolen); > > + if (dd->wc_cookie < 0) > > + ret = -EINVAL; > > don't agree on what wc_cookie will be on error.
Can you elaborate? The one below is the one that starts things, and arch_phys_wc_add() will return 0 on PAT systems. For non-PAT systems it will return a number > 0 *iff* a valid MTRR was added. It will return negative onloy on error then.
The change above is meant to replace a check put in place to see if PAT was enabled. The way we replace this is to ensure that arch_phys_wc_add() returned 0.
If you disagree it'd be great if you can elaborate why.
Luis
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