From: Adam Michaelis <adam.michaelis@rockwellcollins.com>
To: "Popa, Stefan Serban" <StefanSerban.Popa@analog.com>
Cc: "jic23@kernel.org" <jic23@kernel.org>,
"lars@metafoo.de" <lars@metafoo.de>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"knaack.h@gmx.de" <knaack.h@gmx.de>,
"Ardelean, Alexandru" <alexandru.Ardelean@analog.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"charles-antoine.couret@essensium.com"
<charles-antoine.couret@essensium.com>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"clayton.shotwell@rockwellcollins.com"
<clayton.shotwell@rockwellcollins.com>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"pmeerw@pmeerw.net" <pmeerw@pmeerw.net>,
"brandon.maier@rockwellcollins.com"
<brandon.maier@rockwellcollins.com>
Subject: Re: [External] Re: [PATCH v2 3/6] iio: ad7949: Support configuration read-back
Date: Mon, 13 May 2019 09:52:33 -0500 [thread overview]
Message-ID: <CALMrGWWiNq03DidPQQ38gG81jyYuLDLx_ye_LUz-viHVt1c=+w@mail.gmail.com> (raw)
In-Reply-To: <1557741886.29142.3.camel@analog.com>
On Mon, May 13, 2019 at 5:04 AM Popa, Stefan Serban
<StefanSerban.Popa@analog.com> wrote:
>
> On Sb, 2019-05-11 at 11:31 +0100, Jonathan Cameron wrote:
> > [External]
> >
> >
> > On Tue, 7 May 2019 14:53:32 -0500
> > Adam Michaelis <adam.michaelis@collins.com> wrote:
> >
> > >
> > > On Sun, May 5, 2019 at 9:42 AM Jonathan Cameron <jic23@kernel.org>
> > > wrote:
> > > >
> > > >
> > > > On Thu, 2 May 2019 11:14:29 -0500
> > > > Adam Michaelis <adam.michaelis@rockwellcollins.com> wrote:
> > > >
> > > > >
> > > > > Adds device tree parameter to set the configuration read-back bit
> > > > > in the configuration register to tell the AD7949 to include the
> > > > > value of
> > > > > the configuration register at the time the current sample was
> > > > > acquired
> > > > > when reading from the part.
> > > > >
> > > > > Further work must be done to make read-back information available
> > > > > to
> > > > > consumer.
> > > > This needs some explanation of why it is useful at all. I'm certainly
> > > > unclear
> > > > on why it would be useful to configure this at boot time.
> > > >
> > > > Code looks fine.
> > > >
> > > > Jonathan
> > > >
> > > The configuration read-back feature is being maintained from the
> > > original version of this driver. Before adding the device tree entry,
> > > there was no way to change this setting other than debugfs raw access
> > > to the SPI interface, and there is still no access to the returned
> > > configuration data should the feature be enabled. I would be willing
> > > to remove the feature altogether, but wanted to tread softly on
> > > existing features.
> > Ah. Makes sense. My gut feeling is to drop it.
> >
> > Anyone at Analog have a view on this?
> >
> > Thanks,
> >
> > Jonathan
> >
>
> Hi,
>
> It is not obvious to me why this feature would be useful. I would not add
> it.
>
> Regards,
> -Stefan
>
I have removed this feature in V3 of the patch series.
Thank you for the feedback,
Adam
> > >
> > >
> > > Adam
> > > >
> > > > >
> > > > >
> > > > > Signed-off-by: Adam Michaelis <adam.michaelis@rockwellcollins.com>
> > > > > ---
> > > > > V2: Add some defines to reduce use of magic numbers.
> > > > > ---
> > > > > drivers/iio/adc/ad7949.c | 12 +++++++++++-
> > > > > 1 file changed, 11 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > > > > index afc1361af5fb..7820e1097787 100644
> > > > > --- a/drivers/iio/adc/ad7949.c
> > > > > +++ b/drivers/iio/adc/ad7949.c
> > > > > @@ -69,6 +69,7 @@ struct ad7949_adc_spec {
> > > > > * @iio_dev: reference to iio structure
> > > > > * @spi: reference to spi structure
> > > > > * @ref_sel: selected reference voltage source
> > > > > + * @cfg_readback: whether reads will include configuration data
> > > > > * @resolution: resolution of the chip
> > > > > * @cfg: copy of the configuration register
> > > > > * @current_channel: current channel in use
> > > > > @@ -80,6 +81,7 @@ struct ad7949_adc_chip {
> > > > > struct iio_dev *indio_dev;
> > > > > struct spi_device *spi;
> > > > > enum ad7949_ref_sel ref_sel;
> > > > > + bool cfg_readback;
> > > > > u8 resolution;
> > > > > u16 cfg;
> > > > > unsigned int current_channel;
> > > > > @@ -283,7 +285,11 @@ static int ad7949_spi_init(struct
> > > > > ad7949_adc_chip *ad7949_adc)
> > > > > AD7949_CFG_REF_SEL_MASK;
> > > > > adc_config |= (AD7949_CFG_SEQ_DISABLED <<
> > > > > AD7949_CFG_SEQ_SHIFT) &
> > > > > AD7949_CFG_SEQ_MASK;
> > > > > - adc_config |= AD7949_CFG_READBACK_DIS;
> > > > > +
> > > > > + if (ad7949_adc->cfg_readback)
> > > > > + adc_config |= AD7949_CFG_READBACK_EN;
> > > > > + else
> > > > > + adc_config |= AD7949_CFG_READBACK_DIS;
> > > > >
> > > > > ret = ad7949_spi_write_cfg(ad7949_adc,
> > > > > adc_config,
> > > > > @@ -331,6 +337,10 @@ static int ad7949_spi_probe(struct spi_device
> > > > > *spi)
> > > > > indio_dev->num_channels = spec->num_channels;
> > > > > ad7949_adc->resolution = spec->resolution;
> > > > >
> > > > > + ad7949_adc->cfg_readback = of_property_read_bool(
> > > > > + ad7949_adc->indio_dev->dev.of_node,
> > > > > + "adi,cfg-readback");
> > > > > +
> > > > > ret = of_property_read_u32(ad7949_adc->indio_dev-
> > > > > >dev.of_node,
> > > > > "adi,reference-select",
> > > > > &temp);
> > > --
next prev parent reply other threads:[~2019-05-13 14:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-02 16:14 [PATCH v2 1/6] iio: ad7949: Support internal Vref Adam Michaelis
2019-05-02 16:14 ` [PATCH v2 2/6] dt-bindings: iio: ad7949: Add adi,reference-select Adam Michaelis
2019-05-02 16:14 ` [PATCH v2 3/6] iio: ad7949: Support configuration read-back Adam Michaelis
[not found] ` <20190505154227.1735b1b2@archlinux>
[not found] ` <CALMrGWV6rtYQShtm7uBQygtdOpPW30mLnKMxb2Jk8pY68B6yyw@mail.gmail.com>
2019-05-11 10:31 ` Jonathan Cameron
2019-05-13 10:04 ` Popa, Stefan Serban
2019-05-13 14:52 ` Adam Michaelis [this message]
2019-05-24 12:02 ` Couret Charles-Antoine
2019-05-02 16:14 ` [PATCH v2 4/6] dt-bindings: iio: ad7949: Add cfg-readback option Adam Michaelis
2019-05-02 16:14 ` [PATCH v2 5/6] iio: ad7949: Fix SPI interfacing for 14-bit messages Adam Michaelis
2019-05-05 15:06 ` Jonathan Cameron
2019-05-02 16:14 ` [PATCH v2 6/6] iio: ad7949: Fix dummy read cycle placement Adam Michaelis
2019-05-05 14:39 ` [PATCH v2 1/6] iio: ad7949: Support internal Vref Jonathan Cameron
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