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Date: Fri, 17 Mar 2017 17:26:18 +0100
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Liviu Dudau <liviu@dudau.co.uk>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Bjorn Helgaas <helgaas@kernel.org>, Liviu Dudau <Liviu.Dudau@arm.com>,
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Subject: Re: [PATCH 02/20] PCI: fix pci_remap_iospace() remap attribute
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On Fri, Mar 17, 2017 at 10:43:39AM +0000, Liviu Dudau wrote:
> On Fri, Mar 17, 2017 at 01:33:21AM +0100, Luis R. Rodriguez wrote:
> > a) should we then use a Fixes tag for this patch ?
> 
> I'm not aware of issues being reported, but Lorenzo might have more info on this.

Lorenzo ? If not what exactly made you discover this ? If it is a fix, and only 
ARM64 is implicated, seems like a worthy change to consider for stable for the
sake of stable ARM64 kernels. But, that would leave the PCI config space without
a simple 1 liner fix too -- so maybe its not worth it. Distributions wanting
to support ARM64 however would like to carry these changes, so some annotations
such as Fixes should help.

> > b) it does not seem clear what the semantics for pgprot_device() or even
> >    pgprot_noncached(). Can you add some ?
> > 
> > 8b921acfeffdb ("PCI: Add pci_remap_iospace() to map bus I/O resources")
> > 
> > Also this patch claims archs can override this call alone, as its __weak.
> > So is the right thing to do to change pci_remap_iospace() to pgprot_noncached()
> > or is it for archs to add their own pci_remap_iospace()? If so why ? Without
> > proper semantics defined for these helpers this is all fuzzy.
> 
> That was the initial intention, to let arches / platforms overwrite the whole
> pci_remap_iospace(). I guess the reality is that no one needs to overwrite it except
> for the AArch64 quirk, so probably easier to remove the __weak and fix the attributes for arm64.

Sounds much more reasonable to me.

  Luis