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Date:   Sat, 12 Oct 2019 16:38:39 +0000
From:   Dan Robertson <dan@dlrobertson.com>
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     linux-iio@vger.kernel.org,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        devicetree@vger.kernel.org, Hartmut Knaack <knaack.h@gmx.de>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-kernel@vger.kernel.org,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2 2/2] iio: (bma400) add driver for the BMA400
Message-ID: <20191012163839.GB15972@nessie>
References: <20191012035420.13904-1-dan@dlrobertson.com>
 <20191012035420.13904-3-dan@dlrobertson.com>
 <20191012104033.006b33f9@archlinux>
 <20191012153556.GA15972@nessie>
 <20191012173344.7d25fd02@archlinux>
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On Sat, Oct 12, 2019 at 05:33:44PM +0100, Jonathan Cameron wrote:
> On Sat, 12 Oct 2019 15:35:56 +0000
> Dan Robertson <dan@dlrobertson.com> wrote:
> > On Sat, Oct 12, 2019 at 10:40:33AM +0100, Jonathan Cameron wrote:
> > >
> > > Silly question.  Why is soft_reset preferred to sleep mode? =20
> >=20
> > Not a silly question. I actually debated this when initially implementi=
ng the
> > driver. The datasheet describes soft-reset behavior in section 4.9, the
> > following snippet from the datasheet is particularly relevant:
> >=20
> > > The softreset performs a fundamental reset to the device which is lar=
gely
> > > equivalent to a power cycle. Following a delay, all user configuration
> > > settings are overwritten with their default state... =20
> >=20
> > Sleep mode is the default power-mode, so the only real difference would=
 be that
> > the oversampling ratio, sampling frequency, and scale would all be rese=
t to
> > their defaults with a soft-reset. If we just set the power-mode to slee=
p mode,
> > the user configuration registers would be preserved.
> >=20
> > I can add a comment about the behavior of a softreset in bma400_remove.
> I'd just not do it.  That way there is only the putting it to sleep path.
> We normally assume that we don't know the state during startup and aren't
> as careful on remove to make sure things are in a default state.
>=20
> That way you only need a single path in the remove function. If sleep mode
> fails you are probably broken anyway.

Sounds good. That does make remove much easier if the device is not ready f=
or a
command. I'll remove this in the next patchset version.

Cheers,

 - Dan

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