linux-kernel - Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors

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Message-ID: <20140925145538.GN20043@arm.com>
Date:	Thu, 25 Sep 2014 15:55:38 +0100
From:	Will Deacon <will.deacon@....com>
To:	Arnd Bergmann <arnd@...db.de>
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Subject: Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO
 accessors

On Thu, Sep 25, 2014 at 02:15:10PM +0100, Arnd Bergmann wrote:
> On Wednesday 24 September 2014 18:17:19 Will Deacon wrote:
> > This is version three of the series I've originally posted here:
> > 
> >   v1: https://lkml.org/lkml/2014/4/17/269
> >   v2: https://lkml.org/lkml/2014/5/22/468
> > 
> > This is basically just a rebase on top of 3.17-rc6, minus the alpha patch
> > (which was merged into mainline).
> > 
> > I looked at reworking the non-relaxed accessors to imply mmiowb, but it
> > quickly got messy as some architectures (e.g. mips) deliberately keep
> > mmiowb and readX/writeX separate whilst others (e.g. powerpc) don't trust
> > drivers to get mmiowb correct, so add barriers to both. Given that
> > arm/arm64/x86 don't care about mmiowb, I've left that as an exercise for
> > an architecture that does care.
> > 
> > In order to get this lot merged, we probably want to merge the asm-generic
> > patch (1/17) first, so Acks would be much appreciated on the architecture
> > bits.
> > 
> > As before, I've included the original cover letter below, as that describes
> > what I'm trying to do in more detail.
> > 
> 
> I've now applied the parts of your series that are required to have
> every architecture provide all the 'relaxed' accessors to the
> asm-generic tree, on top of Thierry's series.

Brill, thanks Arnd! I'll repost what's left during the next cycle, however
I think you also need to pick the microblaze patch as it includes
<asm-generic/io.h> before defining its relaxed accessors, so I think
you'll get a redefinition warning from the preprocessor.

> I had to change your first patch significantly because all the context
> changed in his patches. See below for the new version. Thierry, can
> you also confirm that this matches up with the intention of your
> series? Since that now adds a separate #ifdef for each symbol, I
> ended up putting the #ifdef for the relaxed version inside of the
> #ifdef for the non-relaxed version, but it could alternatively
> be defined outside of it as well.

I think both work, as I can't find any architectures that define the
relaxed variants but not the non-relaxed versions.

> The entire series of both Thierry's and Will's changes is now in
> git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git
> and should show up in linux-next tomorrow. There are currently
> no conflicts against anything else in linux-next.
> 
> Since we're rather close to the merge window, I'd probably leave
> this in linux-next for a while longer and submit it all for inclusion
> in 3.18 in the second week after 3.17.

Makes sense.

Will
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