Re: [PATCH v5 2/2] iio: adc: ad7944: add driver for AD7944/AD7985/AD7986

[Nuno Sá]

On Mon, 2024-03-04 at 13:48 -0600, David Lechner wrote:
> This adds a driver for the Analog Devices Inc. AD7944, AD7985, and
> AD7986 ADCs. These are a family of pin-compatible ADCs that can sample
> at rates up to 2.5 MSPS.
> 
> The initial driver adds support for sampling at lower rates using the
> usual IIO triggered buffer and can handle all 3 possible reference
> voltage configurations.
> 
> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> ---

LGTM:

Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>



> v5 changes:
> - Dropped "nanoseconds" from comments.
> - Renamed "t" to "timing_spec"
> - Replaced "&spi->dev" with "dev"
> - Fixed logic on optional "ref" regulator
> - Added comment explaining why "cnv" gpio is required
> - Simplified always_turbo assignment
> 
> v4 changes: none
> 
> v3 changes:
> - Replaced _sign with _diff in chip info struct to properly handle
>   pseudo-differential vs. true differential chips. Pseudo-differential chips
>   now just have a voltage0 channel instead of voltage0-voltage1.
> - Fixed not resetting the CNV gpio on error return.
> - Simplified check of adi,spi-mode property now that "multi" is no longer a
>   valid option.
> ---
>  MAINTAINERS              |   1 +
>  drivers/iio/adc/Kconfig  |  10 ++
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad7944.c | 416
> +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 428 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 35f27504632d..7b1a6f2d0c9c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -448,6 +448,7 @@ R:	David Lechner <dlechner@xxxxxxxxxxxx>
>  S:	Supported
>  W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml
> +F:	drivers/iio/adc/ad7944.c
>  
>  ADAFRUIT MINI I2C GAMEPAD
>  M:	Anshul Dalal <anshulusr@xxxxxxxxx>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 0d9282fa67f5..555ac74889f3 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -264,6 +264,16 @@ config AD7923
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad7923.
>  
> +config AD7944
> +	tristate "Analog Devices AD7944 and similar ADCs driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Analog Devices
> +	  AD7944, AD7985, AD7986 ADCs.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad7944
> +
>  config AD7949
>  	tristate "Analog Devices AD7949 and similar ADCs driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index b3c434722364..a0d69b452cca 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_AD7780) += ad7780.o
>  obj-$(CONFIG_AD7791) += ad7791.o
>  obj-$(CONFIG_AD7793) += ad7793.o
>  obj-$(CONFIG_AD7887) += ad7887.o
> +obj-$(CONFIG_AD7944) += ad7944.o
>  obj-$(CONFIG_AD7949) += ad7949.o
>  obj-$(CONFIG_AD799X) += ad799x.o
>  obj-$(CONFIG_AD9467) += ad9467.o
> diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c
> new file mode 100644
> index 000000000000..adb007cdd287
> --- /dev/null
> +++ b/drivers/iio/adc/ad7944.c
> @@ -0,0 +1,416 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Analog Devices AD7944/85/86 PulSAR ADC family driver.
> + *
> + * Copyright 2024 Analog Devices, Inc.
> + * Copyright 2024 BayLibre, SAS
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/string_helpers.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +
> +#define AD7944_INTERNAL_REF_MV		4096
> +
> +struct ad7944_timing_spec {
> +	/* Normal mode max conversion time (t_{CONV}). */
> +	unsigned int conv_ns;
> +	/* TURBO mode max conversion time (t_{CONV}). */
> +	unsigned int turbo_conv_ns;
> +};
> +
> +struct ad7944_adc {
> +	struct spi_device *spi;
> +	/* Chip-specific timing specifications. */
> +	const struct ad7944_timing_spec *timing_spec;
> +	/* GPIO connected to CNV pin. */
> +	struct gpio_desc *cnv;
> +	/* Optional GPIO to enable turbo mode. */
> +	struct gpio_desc *turbo;
> +	/* Indicates TURBO is hard-wired to be always enabled. */
> +	bool always_turbo;
> +	/* Reference voltage (millivolts). */
> +	unsigned int ref_mv;
> +
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the
> +	 * transfer buffers to live in their own cache lines.
> +	 */
> +	struct {
> +		union {
> +			u16 u16;
> +			u32 u32;
> +		} raw;
> +		u64 timestamp __aligned(8);
> +	 } sample __aligned(IIO_DMA_MINALIGN);
> +};
> +
> +static const struct ad7944_timing_spec ad7944_timing_spec = {
> +	.conv_ns = 420,
> +	.turbo_conv_ns = 320,
> +};
> +
> +static const struct ad7944_timing_spec ad7986_timing_spec = {
> +	.conv_ns = 500,
> +	.turbo_conv_ns = 400,
> +};
> +
> +struct ad7944_chip_info {
> +	const char *name;
> +	const struct ad7944_timing_spec *timing_spec;
> +	const struct iio_chan_spec channels[2];
> +};
> +
> +/*
> + * AD7944_DEFINE_CHIP_INFO - Define a chip info structure for a specific chip
> + * @_name: The name of the chip
> + * @_ts: The timing specification for the chip
> + * @_bits: The number of bits in the conversion result
> + * @_diff: Whether the chip is true differential or not
> + */
> +#define AD7944_DEFINE_CHIP_INFO(_name, _ts, _bits, _diff)		\
> +static const struct ad7944_chip_info _name##_chip_info = {		\
> +	.name =
> #_name,							\
> +	.timing_spec = &_ts##_timing_spec,				\
> +	.channels = {							\
> +		{							\
> +			.type = IIO_VOLTAGE,				\
> +			.indexed = 1,					\
> +			.differential = _diff,				\
> +			.channel = 0,					\
> +			.channel2 = _diff ? 1 : 0,			\
> +			.scan_index = 0,				\
> +			.scan_type.sign = _diff ? 's' : 'u',		\
> +			.scan_type.realbits = _bits,			\
> +			.scan_type.storagebits = _bits > 16 ? 32 : 16,	\
> +			.scan_type.endianness = IIO_CPU,		\
> +			.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)	\
> +					| BIT(IIO_CHAN_INFO_SCALE),	\
> +		},							\
> +		IIO_CHAN_SOFT_TIMESTAMP(1),				\
> +	},								\
> +}
> +
> +/* pseudo-differential with ground sense */
> +AD7944_DEFINE_CHIP_INFO(ad7944, ad7944, 14, 0);
> +AD7944_DEFINE_CHIP_INFO(ad7985, ad7944, 16, 0);
> +/* fully differential */
> +AD7944_DEFINE_CHIP_INFO(ad7986, ad7986, 18, 1);
> +
> +/*
> + * ad7944_4wire_mode_conversion - Perform a 4-wire mode conversion and
> acquisition
> + * @adc: The ADC device structure
> + * @chan: The channel specification
> + * Return: 0 on success, a negative error code on failure
> + *
> + * Upon successful return adc->sample.raw will contain the conversion result.
> + */
> +static int ad7944_4wire_mode_conversion(struct ad7944_adc *adc,
> +					const struct iio_chan_spec *chan)
> +{
> +	unsigned int t_conv_ns = adc->always_turbo ? adc->timing_spec-
> >turbo_conv_ns
> +						   : adc->timing_spec-
> >conv_ns;
> +	struct spi_transfer xfers[] = {
> +		{
> +			/*
> +			 * NB: can get better performance from some SPI
> +			 * controllers if we use the same bits_per_word
> +			 * in every transfer.
> +			 */
> +			.bits_per_word = chan->scan_type.realbits,
> +			/*
> +			 * CS has to be high for full conversion time to
> avoid
> +			 * triggering the busy indication.
> +			 */
> +			.cs_off = 1,
> +			.delay = {
> +				.value = t_conv_ns,
> +				.unit = SPI_DELAY_UNIT_NSECS,
> +			},
> +
> +		},
> +		{
> +			.rx_buf = &adc->sample.raw,
> +			.len = BITS_TO_BYTES(chan->scan_type.storagebits),
> +			.bits_per_word = chan->scan_type.realbits,
> +		},
> +	};
> +	int ret;
> +
> +	/*
> +	 * In 4-wire mode, the CNV line is held high for the entire
> conversion
> +	 * and acquisition process.
> +	 */
> +	gpiod_set_value_cansleep(adc->cnv, 1);
> +	ret = spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
> +	gpiod_set_value_cansleep(adc->cnv, 0);
> +
> +	return ret;
> +}
> +
> +static int ad7944_single_conversion(struct ad7944_adc *adc,
> +				    const struct iio_chan_spec *chan,
> +				    int *val)
> +{
> +	int ret;
> +
> +	ret = ad7944_4wire_mode_conversion(adc, chan);
> +	if (ret)
> +		return ret;
> +
> +	if (chan->scan_type.storagebits > 16)
> +		*val = adc->sample.raw.u32;
> +	else
> +		*val = adc->sample.raw.u16;
> +
> +	if (chan->scan_type.sign == 's')
> +		*val = sign_extend32(*val, chan->scan_type.realbits - 1);
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad7944_read_raw(struct iio_dev *indio_dev,
> +			   const struct iio_chan_spec *chan,
> +			   int *val, int *val2, long info)
> +{
> +	struct ad7944_adc *adc = 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 = ad7944_single_conversion(adc, chan, val);
> +		iio_device_release_direct_mode(indio_dev);
> +		return ret;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_VOLTAGE:
> +			*val = adc->ref_mv;
> +
> +			if (chan->scan_type.sign == 's')
> +				*val2 = chan->scan_type.realbits - 1;
> +			else
> +				*val2 = chan->scan_type.realbits;
> +
> +			return IIO_VAL_FRACTIONAL_LOG2;
> +		default:
> +			return -EINVAL;
> +		}
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info ad7944_iio_info = {
> +	.read_raw = &ad7944_read_raw,
> +};
> +
> +static irqreturn_t ad7944_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct ad7944_adc *adc = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = ad7944_4wire_mode_conversion(adc, &indio_dev->channels[0]);
> +	if (ret)
> +		goto out;
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, &adc->sample.raw,
> +					   pf->timestamp);
> +
> +out:
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const char * const ad7944_power_supplies[] = {
> +	"avdd",	"dvdd",	"bvdd", "vio"
> +};
> +
> +static void ad7944_ref_disable(void *ref)
> +{
> +	regulator_disable(ref);
> +}
> +
> +static int ad7944_probe(struct spi_device *spi)
> +{
> +	const struct ad7944_chip_info *chip_info;
> +	struct device *dev = &spi->dev;
> +	struct iio_dev *indio_dev;
> +	struct ad7944_adc *adc;
> +	bool have_refin = false;
> +	struct regulator *ref;
> +	int ret;
> +
> +	/*
> +	 * driver currently only supports the conventional "4-wire" mode and
> +	 * not other special wiring configurations.
> +	 */
> +	if (device_property_present(dev, "adi,spi-mode"))
> +		return dev_err_probe(dev, -EINVAL,
> +				     "adi,spi-mode is not currently
> supported\n");
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	adc = iio_priv(indio_dev);
> +	adc->spi = spi;
> +
> +	chip_info = spi_get_device_match_data(spi);
> +	if (!chip_info)
> +		return dev_err_probe(dev, -EINVAL, "no chip info\n");
> +
> +	adc->timing_spec = chip_info->timing_spec;
> +
> +	/*
> +	 * Some chips use unusual word sizes, so check now instead of waiting
> +	 * for the first xfer.
> +	 */
> +	if (!spi_is_bpw_supported(spi, chip_info-
> >channels[0].scan_type.realbits))
> +		return dev_err_probe(dev, -EINVAL,
> +				"SPI host does not support %d bits per
> word\n",
> +				chip_info->channels[0].scan_type.realbits);
> +
> +	ret = devm_regulator_bulk_get_enable(dev,
> +					    
> ARRAY_SIZE(ad7944_power_supplies),
> +					     ad7944_power_supplies);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "failed to get and enable supplies\n");
> +
> +	/*
> +	 * Sort out what is being used for the reference voltage. Options
> are:
> +	 * - internal reference: neither REF or REFIN is connected
> +	 * - internal reference with external buffer: REF not connected,
> REFIN
> +	 *   is connected
> +	 * - external reference: REF is connected, REFIN is not connected
> +	 */
> +
> +	ref = devm_regulator_get_optional(dev, "ref");
> +	if (IS_ERR(ref)) {
> +		if (PTR_ERR(ref) != -ENODEV)
> +			return dev_err_probe(dev, PTR_ERR(ref),
> +					     "failed to get REF supply\n");
> +
> +		ref = NULL;
> +	}
> +
> +	ret = devm_regulator_get_enable_optional(dev, "refin");
> +	if (ret == 0)
> +		have_refin = true;
> +	else if (ret != -ENODEV)
> +		return dev_err_probe(dev, ret,
> +				     "failed to get and enable REFIN
> supply\n");
> +
> +	if (have_refin && ref)
> +		return dev_err_probe(dev, -EINVAL,
> +				     "cannot have both refin and ref
> supplies\n");
> +
> +	if (ref) {
> +		ret = regulator_enable(ref);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "failed to enable REF
> supply\n");
> +
> +		ret = devm_add_action_or_reset(dev, ad7944_ref_disable, ref);
> +		if (ret)
> +			return ret;
> +
> +		ret = regulator_get_voltage(ref);
> +		if (ret < 0)
> +			return dev_err_probe(dev, ret,
> +					     "failed to get REF voltage\n");
> +
> +		/* external reference */
> +		adc->ref_mv = ret / 1000;
> +	} else {
> +		/* internal reference */
> +		adc->ref_mv = AD7944_INTERNAL_REF_MV;
> +	}
> +
> +	/*
> +	 * CNV gpio is required in 4-wire mode which is the only currently
> +	 * supported mode.
> +	 */
> +	adc->cnv = devm_gpiod_get(dev, "cnv", GPIOD_OUT_LOW);
> +	if (IS_ERR(adc->cnv))
> +		return dev_err_probe(dev, PTR_ERR(adc->cnv),
> +				     "failed to get CNV GPIO\n");
> +
> +	adc->turbo = devm_gpiod_get_optional(dev, "turbo", GPIOD_OUT_LOW);
> +	if (IS_ERR(adc->turbo))
> +		return dev_err_probe(dev, PTR_ERR(adc->turbo),
> +				     "failed to get TURBO GPIO\n");
> +
> +	adc->always_turbo = device_property_present(dev, "adi,always-turbo");
> +
> +	if (adc->turbo && adc->always_turbo)
> +		return dev_err_probe(dev, -EINVAL,
> +			"cannot have both turbo-gpios and adi,always-
> turbo\n");
> +
> +	indio_dev->name = chip_info->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &ad7944_iio_info;
> +	indio_dev->channels = chip_info->channels;
> +	indio_dev->num_channels = ARRAY_SIZE(chip_info->channels);
> +
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> +					      iio_pollfunc_store_time,
> +					      ad7944_trigger_handler, NULL);
> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static const struct of_device_id ad7944_of_match[] = {
> +	{ .compatible = "adi,ad7944", .data = &ad7944_chip_info },
> +	{ .compatible = "adi,ad7985", .data = &ad7985_chip_info },
> +	{ .compatible = "adi,ad7986", .data = &ad7986_chip_info },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ad7944_of_match);
> +
> +static const struct spi_device_id ad7944_spi_id[] = {
> +	{ "ad7944", (kernel_ulong_t)&ad7944_chip_info },
> +	{ "ad7985", (kernel_ulong_t)&ad7985_chip_info },
> +	{ "ad7986", (kernel_ulong_t)&ad7986_chip_info },
> +	{ }
> +
> +};
> +MODULE_DEVICE_TABLE(spi, ad7944_spi_id);
> +
> +static struct spi_driver ad7944_driver = {
> +	.driver = {
> +		.name = "ad7944",
> +		.of_match_table = ad7944_of_match,
> +	},
> +	.probe = ad7944_probe,
> +	.id_table = ad7944_spi_id,
> +};
> +module_spi_driver(ad7944_driver);
> +
> +MODULE_AUTHOR("David Lechner <dlechner@xxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Analog Devices AD7944 PulSAR ADC family driver");
> +MODULE_LICENSE("GPL");
>