linux-kernel - Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

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Message-ID: <20160113100911.GU13633@e106497-lin.cambridge.arm.com>
Date:	Wed, 13 Jan 2016 10:09:11 +0000
From:	liviu.dudau@....com
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Rongrong Zou <zourongrong@...wei.com>,
	Rongrong Zou <zourongrong@...il.com>,
	devicetree@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>,
	Corey Minyard <minyard@....org>, gregkh@...uxfoundation.org,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linuxarm@...wei.com,
	benh@...nel.crashing.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

On Tue, Jan 12, 2016 at 11:54:59PM +0100, Arnd Bergmann wrote:
> On Tuesday 12 January 2016 10:14:18 liviu.dudau@....com wrote:
> > 
> > OK, looking at of_translate_one() comments it looks like a missing "ranges" property is
> > only accepted on PowerPC. I suggest you have an empty "ranges" property in your isa
> > parent node, that will signal to the OF parsing code that the mapping is 1:1. Then have
> > the IPMI node use the reg = <0x0 0xe4 4>; property values instead of reg = <0x1 0xe4 4>;
> > 
> > 
> 
> A missing ranges property means that there is no translation, while an
> empty ranges means a 1:1 translation to the parent bus.
> 
> We really want the former here, as I/O port addresses are not mapped into
> the MMIO space of the parent bus.

Agree. However of_translate_one()'s behaviour doesn't match our expectations and I have no
useful suggestions on what the right behaviour should be.

Best regards,
Liviu

> 
> 	Arnd
> 

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