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

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Date:	Thu, 25 Sep 2014 12:42:15 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Will Deacon <will.deacon@....com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.org, chris@...kel.net, cmetcalf@...era.com,
	davem@...emloft.net, deller@....de, dhowells@...hat.com,
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	jcmvbkbc@...il.com, jesper.nilsson@...s.com, mingo@...hat.com,
	monstr@...str.eu, paulmck@...ux.vnet.ibm.com,
	rdunlap@...radead.org, sam@...nborg.org, schwidefsky@...ibm.com,
	starvik@...s.com, takata@...ux-m32r.org, tglx@...utronix.de,
	tony.luck@...el.com, daniel.thompson@...aro.org,
	broonie@...aro.org, linux@....linux.org.uk
Subject: Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors

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'm definitely happy to merge that first patch in the asm-generic tree, or
have it go through some other tree along with architecture specific patches.
Anything that helps get these functions across all architectures really.

I don't think there is any controversy about whether or not we should
have the functions, or what the default should be on architectures that
don't provide their own, so I wonder why we can't just add the conditional
definitions to linux/io.h and remove the trivial definitions from
architectures afterwards.

	Arnd
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