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Date:   Mon, 14 Oct 2019 13:02:02 +0100
From:   Jonathan Cameron <jonathan.cameron@huawei.com>
To:     Marcelo Schmitt <marcelo.schmitt1@gmail.com>
CC:     <jic23@kernel.org>, <dragos.bogdan@analog.com>,
        <alexandru.ardelean@analog.com>, <stefan.popa@analog.com>,
        <linux-kernel@vger.kernel.org>, <linux-iio@vger.kernel.org>
Subject: Re: [PATCH 1/2] iio: adc: Add driver support for AD7292
Message-ID: <20191014130202.000030d5@huawei.com>
In-Reply-To: <20191013141320.aam4243nnxmofxl4@smtp.gmail.com>
References: <20191013141320.aam4243nnxmofxl4@smtp.gmail.com>
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On Sun, 13 Oct 2019 11:13:22 -0300
Marcelo Schmitt <marcelo.schmitt1@gmail.com> wrote:

> The AD7292 is a 10-bit monitor and control system with ADC, DACs,
> temperature sensor, and GPIOs.
> 
> Configure AD7292 devices in direct access mode, enabling single-ended
> ADC readings.
> 
> Datasheet:
> Link: https://www.analog.com/media/en/technical-documentation/data-sheets/ad7292.pdf
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Hi Marcelo

A few minor bits inline.  Mostly just the DT binding question.

Thanks,

Jonathan

> ---
>  MAINTAINERS              |   7 +
>  drivers/iio/adc/Kconfig  |  10 ++
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad7292.c | 350 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 368 insertions(+)
>  create mode 100644 drivers/iio/adc/ad7292.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 32bf5f8116d0..e78317a5f4f1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -813,6 +813,13 @@ S:	Supported
>  F:	drivers/iio/adc/ad7124.c
>  F:	Documentation/devicetree/bindings/iio/adc/adi,ad7124.txt
>  
> +ANALOG DEVICES INC AD7292 DRIVER
> +M:	Marcelo Schmitt <marcelo.schmitt1@gmail.com>
> +L:	linux-iio@vger.kernel.org
> +W:	http://ez.analog.com/community/linux-device-drivers
> +S:	Supported
> +F:	drivers/iio/adc/ad7292.c
> +
>  ANALOG DEVICES INC AD7606 DRIVER
>  M:	Stefan Popa <stefan.popa@analog.com>
>  L:	linux-iio@vger.kernel.org
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 632b331429c6..02587c990cb5 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -59,6 +59,16 @@ config AD7291
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad7291.
>  
> +config AD7292
> +	tristate "Analog Devices AD7292 ADC driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Analog Devices AD7292
> +	  8 Channel ADC with temperature sensor.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad7292.
> +
>  config AD7298
>  	tristate "Analog Devices AD7298 ADC driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 4779ab3ff8fb..1818f2f66566 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -11,6 +11,7 @@ obj-$(CONFIG_AD7124) += ad7124.o
>  obj-$(CONFIG_AD7173) += ad7173.o
>  obj-$(CONFIG_AD7266) += ad7266.o
>  obj-$(CONFIG_AD7291) += ad7291.o
> +obj-$(CONFIG_AD7292) += ad7292.o
>  obj-$(CONFIG_AD7298) += ad7298.o
>  obj-$(CONFIG_AD738X) += ad738x.o
>  obj-$(CONFIG_AD7768) += ad7768-1.o
> diff --git a/drivers/iio/adc/ad7292.c b/drivers/iio/adc/ad7292.c
> new file mode 100644
> index 000000000000..076bd49a2571
> --- /dev/null
> +++ b/drivers/iio/adc/ad7292.c
> @@ -0,0 +1,350 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Analog Devices AD7292 SPI ADC driver
> + *
> + * Copyright 2019 Analog Devices Inc.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <linux/iio/iio.h>
> +
> +#define ADI_VENDOR_ID 0x0018
> +
> +/* AD7292 registers definition */
> +#define AD7292_REG_VENDOR_ID		0x00
> +#define AD7292_REG_CONF_BANK		0x05
> +#define AD7292_REG_CONV_COMM		0x0E
> +#define AD7292_REG_ADC_CH(x)		(0x10 + (x))
> +
> +/* AD7292 configuration bank subregisters definition */
> +#define AD7292_BANK_REG_VIN_RNG0	0x10
> +#define AD7292_BANK_REG_VIN_RNG1	0x11
> +#define AD7292_BANK_REG_SAMP_MODE	0x12
> +
> +#define AD7292_RD_FLAG_MSK(x)		(BIT(7) | ((x) & 0x3F))
> +
> +/* AD7292_REG_ADC_CONVERSION */
> +#define AD7292_ADC_DATA_MASK		GENMASK(15, 6)
> +#define AD7292_ADC_DATA(x)		FIELD_GET(AD7292_ADC_DATA_MASK, x)
> +
> +/* AD7292_CHANNEL_SAMPLING_MODE */
> +#define AD7292_CH_SAMP_MODE(reg, ch)	((reg >> 8) & BIT(ch))
> +
> +/* AD7292_CHANNEL_VIN_RANGE */
> +#define AD7292_CH_VIN_RANGE(reg, ch)	(reg & BIT(ch))
> +
> +#define AD7291_VOLTAGE_CHAN(_chan)					\
> +{									\
> +	.type = IIO_VOLTAGE,						\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
> +			      BIT(IIO_CHAN_INFO_SCALE),			\
> +	.indexed = 1,							\
> +	.channel = _chan,						\
> +}
> +
> +static const struct iio_chan_spec ad7292_channels[] = {
> +	AD7291_VOLTAGE_CHAN(0),
> +	AD7291_VOLTAGE_CHAN(1),
> +	AD7291_VOLTAGE_CHAN(2),
> +	AD7291_VOLTAGE_CHAN(3),
> +	AD7291_VOLTAGE_CHAN(4),
> +	AD7291_VOLTAGE_CHAN(5),
> +	AD7291_VOLTAGE_CHAN(6),
> +	AD7291_VOLTAGE_CHAN(7)
> +};
> +
> +static const struct iio_chan_spec ad7292_channels_diff[] = {
> +	{
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.indexed = 1,
> +		.differential = 1,
> +		.channel = 0,
> +		.channel2 = 1,
> +	},
> +	AD7291_VOLTAGE_CHAN(2),
> +	AD7291_VOLTAGE_CHAN(3),
> +	AD7291_VOLTAGE_CHAN(4),
> +	AD7291_VOLTAGE_CHAN(5),
> +	AD7291_VOLTAGE_CHAN(6),
> +	AD7291_VOLTAGE_CHAN(7)
> +};
> +
> +struct ad7292_state {
> +	struct spi_device *spi;
> +	struct regulator *reg;
> +	unsigned short vref_mv;
> +	union {
> +		__be16 d16;
> +		u8 d8[2];
> +	} data ____cacheline_aligned;

Given it is a whole cacheline long anyway, I'd be tempted to just have
these as separate fields.

> +};
> +
> +static int ad7292_spi_reg_read(struct ad7292_state *st, unsigned int addr)
> +{
> +	int ret;
> +
> +	st->data.d8[0] = AD7292_RD_FLAG_MSK(addr);
> +
> +	ret = spi_write_then_read(st->spi, st->data.d8, 1, &st->data.d16, 2);
> +	if (ret < 0)
> +		return ret;
> +
> +	return be16_to_cpu(st->data.d16);
> +}
> +
> +static int ad7292_spi_subreg_read(struct ad7292_state *st, unsigned int addr,
> +				  unsigned int sub_addr, unsigned int len)
> +{
> +	unsigned int shift = 16 - (8 * len);
> +	int ret;
> +
> +	st->data.d8[0] = AD7292_RD_FLAG_MSK(addr);
> +	st->data.d8[1] = sub_addr;
> +
> +	ret = spi_write_then_read(st->spi, st->data.d8, 2, &st->data.d16, len);
> +	if (ret < 0)
> +		return ret;
> +
> +	return (be16_to_cpu(st->data.d16) >> shift);
> +}
> +
> +static int ad7292_single_conversion(struct ad7292_state *st,
> +				    unsigned int chan_addr)
> +{
> +	int ret;
> +
> +	struct spi_transfer t[] = {
> +		{
> +			.tx_buf = &st->data,
> +			.len = 4,
> +			.delay_usecs = 6,
> +		}, {
> +			.rx_buf = &st->data.d16,
> +			.len = 2,
> +		},
> +	};
> +
> +	st->data.d8[0] = chan_addr;
> +	st->data.d8[1] = AD7292_RD_FLAG_MSK(AD7292_REG_CONV_COMM);
> +
> +	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	return be16_to_cpu(st->data.d16);
> +}
> +
> +static int ad7292_vin_range_multiplier(struct ad7292_state *st, int channel)
> +{
> +	int samp_mode, range0, range1;
> +	int factor = 1;
> +
> +	/*
> +	 * Every AD7292 ADC channel may have its input range adjusted according
> +	 * to the settings at the ADC sampling mode and VIN range subregisters.
> +	 * For a given channel, the minimum input range is equal to Vref, and it
> +	 * may be increased by a multiplier factor of 2 or 4 according to the
> +	 * following rule:
> +	 * If channel is being sampled wiht respect to AGND:
> +	 *	factor = 4 if VIN range0 and VIN range1 equal 0
> +	 *	factor = 2 if only one of VIN ranges equal 1
> +	 *	factor = 1 if both VIN range0 and VIN range1 equal 1
> +	 * If channel is being sampled with respect to AVDD:
> +	 *	factor = 4 if VIN range0 and VIN range1 equal 0
> +	 *	Behavior is undefined if any of VIN range doesn't equal 0
> +	 */
> +
> +	samp_mode = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
> +					   AD7292_BANK_REG_SAMP_MODE, 2);
> +
> +	if (samp_mode < 0)
> +		return samp_mode;
> +
> +	range0 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
> +					AD7292_BANK_REG_VIN_RNG0, 2);
> +
> +	if (range0 < 0)
> +		return range0;
> +
> +	range1 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
> +					AD7292_BANK_REG_VIN_RNG1, 2);
> +
> +	if (range1 < 0)
> +		return range1;
> +
> +	if (AD7292_CH_SAMP_MODE(samp_mode, channel)) {
> +		/* Sampling with respect to AGND */
> +		if (!AD7292_CH_VIN_RANGE(range0, channel))
> +			factor *= 2;
> +
> +		if (!AD7292_CH_VIN_RANGE(range1, channel))
> +			factor *= 2;
> +
> +	} else {
> +		/* Sampling with respect to AVDD */
> +		if (AD7292_CH_VIN_RANGE(range0, channel) ||
> +		    AD7292_CH_VIN_RANGE(range1, channel))
> +			return -EPERM;
> +
> +		factor = 4;
> +	}
> +
> +	return factor;
> +}
> +
> +static int ad7292_read_raw(struct iio_dev *indio_dev,
> +			   const struct iio_chan_spec *chan,
> +			   int *val, int *val2, long info)
> +{
> +	struct ad7292_state *st = iio_priv(indio_dev);
> +	unsigned int ch_addr;
> +	int ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		ch_addr = AD7292_REG_ADC_CH(chan->channel);
> +		ret = ad7292_single_conversion(st, ch_addr);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = AD7292_ADC_DATA(ret);
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		/*
> +		 * To convert a raw value to standard units, the IIO defines
> +		 * this formula: Scaled value = (raw + offset) * scale.
> +		 * For the scale to be a correct multiplier for (raw + offset),
> +		 * it must be calculated as the input range divided by the
> +		 * number of possible distinct input values. Given the ADC data
> +		 * is 10 bit long, it may assume only 2^10 distinct values.
> +		 * Hence, scale = range / 2^10. The IIO_VAL_FRACTIONAL_LOG2
> +		 * return type indicates to the IIO API to divide *val by 2 to
> +		 * the power of *val2 when returning from read_raw.
> +		 */
> +
> +		*val = regulator_get_voltage(st->reg);
> +		if (*val < 0)
> +			*val = st->vref_mv;
> +		else
> +			*val /= 1000;
> +
> +		ret = ad7292_vin_range_multiplier(st, chan->channel);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val *= ret;
> +		*val2 = 10;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info ad7292_info = {
> +	.read_raw = ad7292_read_raw,
> +};
> +
> +static void ad7292_regulator_disable(void *data)
> +{
> +	struct ad7292_state *st = data;
> +
> +	regulator_disable(st->reg);
> +}
> +
> +static int ad7292_probe(struct spi_device *spi)
> +{
> +	struct ad7292_state *st;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	st->spi = spi;
> +
> +	ret = ad7292_spi_reg_read(st, AD7292_REG_VENDOR_ID);
> +	if (ret != ADI_VENDOR_ID) {
> +		dev_err(&spi->dev, "Wrong vendor id 0x%x\n", ret);
> +		return -EINVAL;
> +	}
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
> +	if (!IS_ERR(st->reg)) {
> +		ret = regulator_enable(st->reg);
> +		if (ret) {
> +			dev_err(&spi->dev,
> +				"Failed to enable external vref supply\n");
> +			return ret;
> +		}
> +
> +		ret = devm_add_action_or_reset(&spi->dev,
> +					       ad7292_regulator_disable, st);
> +		if (ret) {
> +			regulator_disable(st->reg);
> +			return ret;
> +		}
> +
> +		ret = regulator_get_voltage(st->reg);
> +		if (ret < 0)
> +			return ret;

We get the voltage here, but then I think we throw it away by rereading it
each time above.  No need to get it in both places.

> +
> +		st->vref_mv = ret / 1000;
> +	} else {

	Perhaps add a comment here to say this is the internal reference.

> +		st->vref_mv = 1250;
> +	}
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &ad7292_info;
> +
> +	ret = of_property_read_bool(spi->dev.of_node, "diff-channels");

I mention in review of the dt patch that this should use the generic
binding support for specifying differential channels.

> +	if (ret) {
> +		indio_dev->num_channels = ARRAY_SIZE(ad7292_channels_diff);
> +		indio_dev->channels = ad7292_channels_diff;
> +	} else {
> +		indio_dev->num_channels = ARRAY_SIZE(ad7292_channels);
> +		indio_dev->channels = ad7292_channels;
> +	}
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct spi_device_id ad7292_id_table[] = {
> +	{ "ad7292", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, ad7292_id_table);
> +
> +static const struct of_device_id ad7292_of_match[] = {
> +	{ .compatible = "adi,ad7292" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, ad7292_of_match);
> +
> +static struct spi_driver ad7292_driver = {
> +	.driver = {
> +		.name = "ad7292",
> +		.of_match_table = ad7292_of_match,
> +	},
> +	.probe = ad7292_probe,
> +	.id_table = ad7292_id_table,
> +};
> +module_spi_driver(ad7292_driver);
> +
> +MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt1@gmail.com>");
> +MODULE_DESCRIPTION("Analog Devices AD7292 ADC driver");
> +MODULE_LICENSE("GPL v2");