Date:   Tue, 15 Oct 2019 13:45:11 -0300
From:   Marcelo Schmitt <marcelo.schmitt1@...il.com>
To:     Jonathan Cameron <jonathan.cameron@...wei.com>
Cc:     jic23@...nel.org, dragos.bogdan@...log.com,
        alexandru.ardelean@...log.com, stefan.popa@...log.com,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH 1/2] iio: adc: Add driver support for AD7292

Hi Jonathan,

Thanks for the review. I'll send a v2 soon.

On 10/14, Jonathan Cameron wrote:
> On Sun, 13 Oct 2019 11:13:22 -0300
> Marcelo Schmitt <marcelo.schmitt1@...il.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@...il.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@...il.com>
> > +L:	linux-iio@...r.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@...log.com>
> >  L:	linux-iio@...r.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@...il.com>");
> > +MODULE_DESCRIPTION("Analog Devices AD7292 ADC driver");
> > +MODULE_LICENSE("GPL v2");
> 
> 

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