linux-kernel - Re: [PATCH v2 00/18] Cross-architecture definitions of relaxed MMIO accessors

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Message-ID: <1401222210.20915.79.camel@pasglop>
Date:	Wed, 28 May 2014 06:23:30 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Will Deacon <will.deacon@....com>
Cc:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"monstr@...str.eu" <monstr@...str.eu>,
	"dhowells@...hat.com" <dhowells@...hat.com>,
	"broonie@...aro.org" <broonie@...aro.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 00/18] Cross-architecture definitions of relaxed MMIO
 accessors

On Tue, 2014-05-27 at 20:34 +0100, Will Deacon wrote:

> Do you mean the io{read,write} functions? Funnily enough, they're already
> relaxed on ARM if you go by the semantics I've proposed. That implies we at
> least need some Documentation to that effect...
> 
> What do you do on ppc?

They are not supposed to be relaxed. If they are, you probably have a
whole lot of busted drivers :-)

They have the same semantics as readl/writel for memory and as inb/outb
for IO space, they just allow to hide the "type" (memory vs. IO) from
most of the driver code.

We probably need to create a set of _relaxed variants.

Cheers,
Ben.


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