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Date:   Sat, 8 Apr 2023 13:31:33 +0200
From:   Patrik =?iso-8859-1?Q?Dahlstr=F6m?= <risca@dalakolonin.se>
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        letux-kernel@openphoenux.org, kernel@pyra-handheld.com,
        pgoudagunta@nvidia.com, hns@goldelico.com, lars@metafoo.de,
        linux-omap@vger.kernel.org
Subject: Re: [PATCH v3 6/7] iio: adc: palmas: add support for iio threshold
 events
Message-ID: <20230408113133.GB141200@dalakolonin.se>
References: <20230405212233.4167986-1-risca@dalakolonin.se>
 <20230405212233.4167986-7-risca@dalakolonin.se>
 <20230407181947.667614ed@jic23-huawei>
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On Fri, Apr 07, 2023 at 06:19:47PM +0100, Jonathan Cameron wrote:
> On Wed,  5 Apr 2023 23:22:32 +0200
> Patrik Dahlstr=F6m <risca@dalakolonin.se> wrote:
>=20
> > The palmas gpadc block has support for monitoring up to 2 ADC channel=
s
> > and issue an interrupt if they reach past a set threshold. This chang=
e
> > hooks into the IIO events system and exposes to userspace the ability=
 to
> > configure these threshold values for each channel, but only allow up =
to
> > 2 such thresholds to be enabled at any given time. Trying to enable a
> > third channel will result in an error.
> >=20
> > Userspace is expected to input calibrated, as opposed to raw, values =
as
> > threshold. However, it is not enough to do the opposite of what is do=
ne
> > when converting the other way around. To account for tolerances in th=
e
> > ADC, the calculated raw threshold should be adjusted based on the ADC
> > specifications for the device. These specifications include the integ=
ral
> > nonlinearity (INL), offset, and gain error. To adjust the high
> > threshold, use the following equation:
> >=20
> >   (calibrated value + INL) * Gain error + offset =3D maximum value  [=
1]
> >=20
> > Likewise, use the following equation for the low threshold:
> >=20
> >   (calibrated value - INL) * Gain error - offset =3D minimum value
> >=20
> > The gain error is a combination of gain error, as listed in the
> > datasheet, and gain error drift due to temperature and supply. The ex=
act
> > values for these specifications vary between palmas devices. This pat=
ch
> > sets the values found in TWL6035, TWL6037 datasheet.
> >=20
> > [1] TI Application Report, SLIA087A, Guide to Using the GPADC in
> >     TPS65903x, TPS65917-Q1, TPS65919-Q1, and TPS65916 Devices.
> >=20
> > Signed-off-by: Patrik Dahlstr=F6m <risca@dalakolonin.se>
> Hi Patrik,
>=20
> A few really trivial formatting things inline. If we don't end up
> with a v4 for other reasons I can tidy this stuff up whilst applying.

I'll send in a v4 later today :)

>=20
> Jonathan
>=20
>=20