linux-kernel - Re: [PATCH v2 3/5] arm64: Juno: Add memory mapped timer node

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Date:	Tue, 19 May 2015 13:58:03 +0100
From:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
To:	Liviu Dudau <Liviu.Dudau@....com>
Cc:	Mark Rutland <Mark.Rutland@....com>,
	devicetree <devicetree@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Olof Johansson <olof@...om.net>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/5] arm64: Juno: Add memory mapped timer node

On Tue, 2015-05-19 at 12:31 +0100, Liviu Dudau wrote:
> On Tue, May 19, 2015 at 11:56:43AM +0100, Jon Medhurst (Tixy) wrote:
> > On Mon, 2015-05-18 at 18:28 +0100, Liviu Dudau wrote:
> > > Juno based boards have a memory mapped timer @ 0x2a810000. This
> > > is disabled on r0 version of the board due to an SoC errata.
> > 
> > So wouldn't it make more sense then to disable it in the dts for r0? As
> > it is, you disable it in the common file below then have to later
> > re-enable it in juno-r1.dts.
> 
> From what I have seen in the existing DTs the preffer approach seems to be of
> disabling by default the node declared in the common files and enable
> it in the DT that makes use of it.

Yes, I does look that way, and I agree consistency usually wins out over
any arguments over log or obviousness.

> If there is any guidance on how to describe this sort of situations I
> would really love to read it.

I know of none, but I'd speculate the principal we've discovered is to
fail safe and have potentially absent or broken hardware disabled by
default.

-- 
Tixy

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