linux-kernel - Re: [PATCH v2 3/4] dt-bindings: mfd: Add Delta TN48M CPLD drivers bindings

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Message-ID: <20210602100349.GG2173308@dell>
Date:   Wed, 2 Jun 2021 11:03:49 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Robert Marko <robert.marko@...tura.hr>
Cc:     Michael Walle <michael@...le.cc>, Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luka Perkov <luka.perkov@...tura.hr>, jmp@...phyte.org,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Donald Buczek <buczek@...gen.mpg.de>
Subject: Re: [PATCH v2 3/4] dt-bindings: mfd: Add Delta TN48M CPLD drivers
 bindings

On Wed, 02 Jun 2021, Robert Marko wrote:

> On Tue, Jun 1, 2021 at 4:48 PM Lee Jones <lee.jones@...aro.org> wrote:
> >
> > On Tue, 01 Jun 2021, Lee Jones wrote:
> >
> > > On Tue, 01 Jun 2021, Michael Walle wrote:
> > >
> > > > Am 2021-06-01 10:19, schrieb Lee Jones:
> > > > > Why do you require one single Regmap anyway?  Are they register banks
> > > > > not neatly separated on a per-function basis?
> > > >
> > > > AFAIK you can only have one I2C device driver per device, hence the
> > > > simple-mfd-i2c.
> > >
> > > Sorry, can you provide more detail.
> >
> > I'd still like further explanation to be sure, but if you mean what I
> > think you mean then, no, I don't think that's correct.
> >
> > The point of simple-mfd-i2c is to provide an I2C device offering
> > multiple functions, but does so via a non-separated/linear register-
> > set, with an entry point and an opportunity to register its interwoven
> > bank of registers via Regmap.
> >
> > However, if you can get away with not registering your entire register
> > set as a single Regmap chunk, then all the better.  This will allow
> > you to use the OF provided 'simple-mfd' compatible instead.
> >
> > Now, if you're talking about Regmap not supporting multiple
> > registrations with only a single I2C address, this *may* very well be
> > the case, but IIRC, I've spoken to Mark about this previously and he
> > said the extension to make this possible would be trivial.
> 
> This is my understanding, that you cannot have multiple regmap registrations
> with on the same I2C address.
> At least that is how it was the last time I tested.
> That is why I went the MFD way.

I've just clarified with Mark.

There does not appear to be such a restriction.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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