linux-kernel - Re: [PATCH v6 5/9] dt-bindings: ARM: document marvell,ecc-enable binding

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Message-ID: <20181109114818.GB30658@n2100.armlinux.org.uk>
Date:   Fri, 9 Nov 2018 11:48:19 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Borislav Petkov <bp@...en8.de>, jlu@...gutronix.de,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        DTML <devicetree@...r.kernel.org>, linux-edac@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v6 5/9] dt-bindings: ARM: document marvell,ecc-enable
 binding

On Fri, Nov 09, 2018 at 12:40:06PM +0100, Arnd Bergmann wrote:
> On Fri, Nov 9, 2018 at 8:04 AM Chris Packham
> <chris.packham@...iedtelesis.co.nz> wrote:
> >
> > Add documentation for the marvell,ecc-enable and marvell,ecc-disable
> > properties which can be used to enable/disable ECC on the Marvell aurora
> > cache.
> >
> > Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> > ---
> 
> Why do you need both enable and disable? Wouldn't one of them be enough here?

It isn't an "on when ecc-enable is present, off when not" because the
current behaviour is to preserve these bits in the control register.

If we were to implement it as "if no ecc-enable property, turn off
ECC" then that would drastically change the behaviour - systems which
were configured for ECC suddenly lose ECC support.

Since we don't know which have it and which don't, we can't implement
the option like that.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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