Re: [PATCH v2 1/4] iio: adc: ad7887: convert dual-channel mode to DT/ACPI

From: Alexandru Ardelean <ardeleanalex@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Alexandru Ardelean <alexandru.ardelean@analog.com>,
	LKML <linux-kernel@vger.kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	linux-iio <linux-iio@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2 1/4] iio: adc: ad7887: convert dual-channel mode to DT/ACPI
Date: Fri, 27 Nov 2020 14:02:47 +0200	[thread overview]
Message-ID: <CA+U=DsprS5V5LXROP4m4iuWexH9aZir-+DJKWZ4kcgKLS86+Tg@mail.gmail.com> (raw)
In-Reply-To: <20201121153653.568c7344@archlinux>

On Sat, Nov 21, 2020 at 5:38 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Thu, 19 Nov 2020 12:07:45 +0200
> Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
>
> > This change converts the configuration of the dual-channel mode from the
> > old platform-data, to the device_property_present() function, which
> > supports both device-tree and ACPI configuration setups.
> >
> > With this change the old platform_data include of the driver can be
> > removed.
> >
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
>
> Hi Alexandru,
>
> The set looks good in general, but there is a an oddity in the driver.
> If we don't provide the vref regulator, then the scale is set to reflect
> the internal 2.5V reference.  Fiven the external reference only
> works by overdriving the 2.5V (must be higher than that to have
> an effect) I guess we could in theory clamp it to a minimum of
> 2.5V but anyone wiring up less than that would have built a crazy board
> so we can probably ignore it.
>
> However, as I read the datasheet in dual channel mode it should be set
> to VDD not 2.5V.  Right now you could make it work in a DT file
> by setting VREF==VDD regulator but that's inelegant.
>
> If you agree with my logic, perhaps a follow up patch?

I haven't managed to get around to this one.
Will try next week.

>
> Jonathan
>
>
> > ---
> >
> > I'm wondering if this changeset is what was in mind here:
> >  https://lore.kernel.org/linux-iio/CA+U=DsqF5tu8Be9KXeyCWD2uHvV688Nc3n=z_Xi2J6H6DFJPRQ@mail.gmail.com/T/#mbe72e4da3acea3899d0d35402ea81e52a9bc34e6
> > This driver could have been simplified/reduced a whole lot more, but I'm
> > not sure about it. It's a bit of patch-noise, and later
> >
> > Changelog v1 -> v2:
> > * dropped patch 'iio: adc: ad7887: convert driver to full DT probing'
> >   not adding the device_get_match_data() logic anymore
> > * added patch 'iio: adc: ad7887: remove matching code from driver'
> >   hooking the chip info directly to AD7887
> > * added patch 'iio: adc: ad7887: add OF match table'
> >   this just adds an OF table for DT and ACPI
> >
> >  drivers/iio/adc/ad7887.c             | 10 +++++-----
> >  include/linux/platform_data/ad7887.h | 21 ---------------------
> >  2 files changed, 5 insertions(+), 26 deletions(-)
> >  delete mode 100644 include/linux/platform_data/ad7887.h
> >
> > diff --git a/drivers/iio/adc/ad7887.c b/drivers/iio/adc/ad7887.c
> > index 4f6f0e0e03ee..06f684c053a0 100644
> > --- a/drivers/iio/adc/ad7887.c
> > +++ b/drivers/iio/adc/ad7887.c
> > @@ -23,8 +23,6 @@
> >  #include <linux/iio/trigger_consumer.h>
> >  #include <linux/iio/triggered_buffer.h>
> >
> > -#include <linux/platform_data/ad7887.h>
> > -
> >  #define AD7887_REF_DIS               BIT(5)  /* on-chip reference disable */
> >  #define AD7887_DUAL          BIT(4)  /* dual-channel mode */
> >  #define AD7887_CH_AIN1               BIT(3)  /* convert on channel 1, DUAL=1 */
> > @@ -241,9 +239,9 @@ static void ad7887_reg_disable(void *data)
> >
> >  static int ad7887_probe(struct spi_device *spi)
> >  {
> > -     struct ad7887_platform_data *pdata = spi->dev.platform_data;
> >       struct ad7887_state *st;
> >       struct iio_dev *indio_dev;
> > +     bool dual_mode;
> >       uint8_t mode;
> >       int ret;
> >
> > @@ -286,7 +284,9 @@ static int ad7887_probe(struct spi_device *spi)
> >       mode = AD7887_PM_MODE4;
> >       if (!st->reg)
> >               mode |= AD7887_REF_DIS;
> > -     if (pdata && pdata->en_dual)
> > +
> > +     dual_mode = device_property_present(&spi->dev, "adi,dual-channel-mode");
> > +     if (dual_mode)
> >               mode |= AD7887_DUAL;
> >
> >       st->tx_cmd_buf[0] = AD7887_CH_AIN0 | mode;
> > @@ -298,7 +298,7 @@ static int ad7887_probe(struct spi_device *spi)
> >       spi_message_init(&st->msg[AD7887_CH0]);
> >       spi_message_add_tail(&st->xfer[0], &st->msg[AD7887_CH0]);
> >
> > -     if (pdata && pdata->en_dual) {
> > +     if (dual_mode) {
> >               st->tx_cmd_buf[2] = AD7887_CH_AIN1 | mode;
> >
> >               st->xfer[1].rx_buf = &st->data[0];
> > diff --git a/include/linux/platform_data/ad7887.h b/include/linux/platform_data/ad7887.h
> > deleted file mode 100644
> > index 9b4dca6ae70b..000000000000
> > --- a/include/linux/platform_data/ad7887.h
> > +++ /dev/null
> > @@ -1,21 +0,0 @@
> > -/* SPDX-License-Identifier: GPL-2.0-or-later */
> > -/*
> > - * AD7887 SPI ADC driver
> > - *
> > - * Copyright 2010 Analog Devices Inc.
> > - */
> > -#ifndef IIO_ADC_AD7887_H_
> > -#define IIO_ADC_AD7887_H_
> > -
> > -/**
> > - * struct ad7887_platform_data - AD7887 ADC driver platform data
> > - * @en_dual: Whether to use dual channel mode. If set to true AIN1 becomes the
> > - *   second input channel, and Vref is internally connected to Vdd. If set to
> > - *   false the device is used in single channel mode and AIN1/Vref is used as
> > - *   VREF input.
> > - */
> > -struct ad7887_platform_data {
> > -     bool en_dual;
> > -};
> > -
> > -#endif /* IIO_ADC_AD7887_H_ */
>