Re: [PATCH 2/2] iio: adc: ad7380: new driver for AD7380 ADCs

[Nuno Sá]

Hi David,

minor stuff from me...

On Fri, 2023-12-08 at 09:51 -0600, David Lechner wrote:
> This adds a new driver for the AD7380 family ADCs.
> 
> The driver currently implements basic support for the AD7380, AD7381,
> AD7383, and AD7384 2-channel differential ADCs. Support for additional
> single-ended and 4-channel chips that use the same register map as well
> as additional features of the chip will be added in future patches.
> 
> Co-developed-by: Stefan Popa <stefan.popa@xxxxxxxxxx>
> Signed-off-by: Stefan Popa <stefan.popa@xxxxxxxxxx>
> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> ---
>  MAINTAINERS              |   1 +
>  drivers/iio/adc/Kconfig  |  16 ++
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad7380.c | 467
> +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 485 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e2a998be5879..5a54620a31b8 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -438,6 +438,7 @@ S:	Supported
>  W:	
> https://wiki.analog.com/resources/tools-software/linux-drivers/iio-adc/ad738x
>  W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml
> +F:	drivers/iio/adc/ad7380.c
>  
>  AD7877 TOUCHSCREEN DRIVER
>  M:	Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 35f9867da12c..cbfd626712e3 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -122,6 +122,22 @@ config AD7298
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad7298.
>  
> +config AD7380
> +	tristate "Analog Devices AD7380 ADC driver"
> +	depends on SPI_MASTER
> +	select IIO_BUFFER
> +	select IIO_TRIGGER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  AD7380 is a family of simultaneous sampling ADCs that share the
> same
> +	  SPI register map and have similar pinouts.
> +
> +	  Say yes here to build support for Analog Devices AD7380 ADC and
> +	  similar chips.
> +
> +	  To compile this driver as a module, choose M here: the module will
> be
> +	  called ad7380.
> +
>  config AD7476
>  	tristate "Analog Devices AD7476 1-channel ADCs driver and other
> similar devices from AD and TI"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index bee11d442af4..e046d8004f41 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_AD7291) += ad7291.o
>  obj-$(CONFIG_AD7292) += ad7292.o
>  obj-$(CONFIG_AD7298) += ad7298.o
>  obj-$(CONFIG_AD7923) += ad7923.o
> +obj-$(CONFIG_AD7476) += ad7380.o
>  obj-$(CONFIG_AD7476) += ad7476.o
>  obj-$(CONFIG_AD7606_IFACE_PARALLEL) += ad7606_par.o
>  obj-$(CONFIG_AD7606_IFACE_SPI) += ad7606_spi.o
> diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
> new file mode 100644
> index 000000000000..6a5ec59bd1fd
> --- /dev/null
> +++ b/drivers/iio/adc/ad7380.c
> @@ -0,0 +1,467 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Analog Devices AD738x Simultaneous Sampling SAR ADCs
> + *
> + * Copyright 2017 Analog Devices Inc.
> + * Copyright 2023 BayLibre, SAS
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/cleanup.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
> +#include <linux/spi/spi.h>
> +#include <linux/sysfs.h>
> +
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +
> 

...

> +
> +static int ad7380_debugfs_reg_access(struct iio_dev *indio_dev, u32 reg,
> +				     u32 writeval, u32 *readval)
> +{
> +	struct ad7380_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;
> +

potential controversial take: do we really need locking in here? regmap already
has it's own lock (I think you're not disabling it) and if someone plays with
registers it shouldn't while buffering, well... This is a debug interface so I
would probably not worry much. One could anyways for write stuff by going
directly to regmap :)

That said, fine to be as-is from my side (just wanted to take it out of my
system :))...

> +	if (readval)
> +		ret = regmap_read(st->regmap, reg, readval);
> +	else
> +		ret = regmap_write(st->regmap, reg, writeval);
> +
> +	iio_device_release_direct_mode(indio_dev);
> +
> +	return ret;
> +}
> +
> +static irqreturn_t ad7380_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct ad7380_state *st = iio_priv(indio_dev);
> +	struct spi_transfer xfer = {
> +		.bits_per_word = st->chip_info-
> >channels[0].scan_type.realbits,
> +		.len = 4,
> +		.rx_buf = &st->scan_data,
> +	};
> +	int ret;
> +
> +	ret = spi_sync_transfer(st->spi, &xfer, 1);
> +
> +	if (ret == 0)
> +		iio_push_to_buffers_with_timestamp(indio_dev, &st->scan_data,
> +						   pf->timestamp);
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int ad7380_read_direct(struct ad7380_state *st,
> +			      struct iio_chan_spec const *chan, int *val)
> +{
> +	struct spi_transfer xfers[] = {
> +		/* toggle CS (no data xfer) to trigger a conversion */
> +		{
> +			.speed_hz = AD7380_REG_WR_SPEED_HZ,
> +			.bits_per_word = chan->scan_type.realbits,
> +			.delay = {
> +				.value = 190, /* t[CONVERT] */
> +				.unit = SPI_DELAY_UNIT_NSECS,
> +			},
> +			.cs_change = 1,
> +			.cs_change_delay = {
> +				.value = 10, /* t[CSH] */
> +				.unit = SPI_DELAY_UNIT_NSECS,
> +			},
> +		},
> +		/* then read both channels */
> +		{
> +			.speed_hz = AD7380_REG_WR_SPEED_HZ,
> +			.bits_per_word = chan->scan_type.realbits,
> +			.rx_buf = &st->rx[0],
> +			.len = 4,
> +		},
> +	};
> +	int ret;
> +
> +	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = sign_extend32(st->rx[chan->scan_index],
> +			     chan->scan_type.realbits - 1);
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad7380_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long info)
> +{
> +	struct ad7380_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = iio_device_claim_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
> +
> +		ret = ad7380_read_direct(st, chan, val);
> +		iio_device_release_direct_mode(indio_dev);
> +
> +		return ret;
> +	case IIO_CHAN_INFO_SCALE:
> +		if (st->vref) {
> +			ret = regulator_get_voltage(st->vref);

nit: I wonder how likely it is for vref to change at runtime...

> +			if (ret < 0)
> +				return ret;
> +
> +			*val = ret / 1000;
> +		} else {
> +			*val = AD7380_INTERNAL_REF_MV;
> +		}
> +
> +		*val2 = chan->scan_type.realbits;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info ad7380_info = {
> +	.read_raw = &ad7380_read_raw,
> +	.debugfs_reg_access = &ad7380_debugfs_reg_access,
> +};
> +
> +static int ad7380_init(struct ad7380_state *st)
> +{
> +	int ret;
> +
> +	/* perform hard reset */
> +	ret = regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2,
> +				 AD7380_CONFIG2_RESET,
> +				 FIELD_PREP(AD7380_CONFIG2_RESET,
> +					    AD7380_CONFIG2_RESET_HARD));
> +	if (ret < 0)
> +		return ret;
> +
> +
> +	/* select internal or external reference voltage */
> +	ret = regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG1,
> +				 AD7380_CONFIG1_REFSEL,
> +				 FIELD_PREP(AD7380_CONFIG1_REFSEL, !!st-
> >vref));
> +	if (ret < 0)
> +		return ret;
> +
> +	/* SPI 1-wire mode */
> +	return regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2,
> +				  AD7380_CONFIG2_SDO,
> +				  FIELD_PREP(AD7380_CONFIG2_SDO, 1));
> +}
> +
> +static void ad7380_release_regulator(void *p)
> +{
> +	struct regulator *reg = p;
> +
> +	regulator_disable(reg);
> +}
> +
> +static int ad7380_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ad7380_state *st;
> +	const char *str_val;
> +	int ret;
> +
> +	ret = device_property_read_string(&spi->dev, "adi,sdo-mode",
> &str_val);
> +	if (ret < 0)
> +		return dev_err_probe(&spi->dev, ret,
> +				     "Failed to read adi,sdo-mode
> property\n");
> +
> +	if (strcmp(str_val, "1-wire"))
> +		return dev_err_probe(&spi->dev, -EINVAL,
> +				     "Only 1-wire SDO is supported\n");
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	st->spi = spi;
> +	st->chip_info = spi_get_device_match_data(spi);
> +

if (!st->chip_info) ?

> +	st->vref = devm_regulator_get_optional(&spi->dev, "refio");
> +	if (IS_ERR(st->vref)) {
> +		/*
> +		 * If there is no REFIO supply, then it means that we are
> using
> +		 * the internal 2.5V reference.
> +		 */
> +		if (PTR_ERR(st->vref) == -ENODEV)
> +			st->vref = NULL;
> +		else
> +			return dev_err_probe(&spi->dev, PTR_ERR(st->vref),
> +					     "Failed to get refio
> regulator\n");
> +	}
> +
> +	if (st->vref) {
> +		ret = regulator_enable(st->vref);
> +		if (ret)
> +			return ret;
> +
> +		ret = devm_add_action_or_reset(&spi->dev,
> ad7380_release_regulator,
> +					       st->vref);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	st->regmap = devm_regmap_init(&spi->dev, NULL, st,
> &ad7380_regmap_config);
> +	if (IS_ERR(st->regmap))
> +		return dev_err_probe(&spi->dev, PTR_ERR(st->regmap),
> +				     "failed to allocate register map\n");
> +

Could we instead have a custom regmap_bus instead of bypass regmap with
reg_read() and reg_write()?
> +
> +	indio_dev->channels = st->chip_info->channels;
> +	indio_dev->num_channels = st->chip_info->num_channels;
> +	indio_dev->dev.parent = &spi->dev;

no need to assign parent (the core does it for you)...

- Nuno Sá