Re: [PATCHv2] iio: adc: Add Maxim MAX11100 driver

[Jonathan Cameron <jic23@kernel.org>]

On 13/12/16 12:37, Jacopo Mondi wrote:
> Add IIO driver for Maxim MAX11100 single-channel ADC.
> Add DT bindings documentation.
> 
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
A quick process related thing.  Please don't post a new
version of a driver as a reply to an old version. It very rapidly
leads to deep and difficult to follow threads.

Much easier to just start a new thread.

> ---
> 
> v1 -> v2:
>     - incorporated pmeerw's review comments
>     - retrieve vref from dts and use that to convert read_raw result
>       to mV
>     - add device tree bindings documentation
> 
> ---
>  .../devicetree/bindings/iio/adc/max11100.txt       |  17 +++
>  drivers/iio/adc/Kconfig                            |   9 ++
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/max11100.c                         | 166 +++++++++++++++++++++
>  4 files changed, 193 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/max11100.txt
>  create mode 100644 drivers/iio/adc/max11100.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/max11100.txt b/Documentation/devicetree/bindings/iio/adc/max11100.txt
> new file mode 100644
> index 0000000..6877c11
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/max11100.txt
> @@ -0,0 +1,17 @@
> +* Maxim max11100 Analog to Digital Converter (ADC)
> +
> +Required properties:
> +  - compatible: Should be "maxim,max11100"
> +  - vref-supply: phandle to the regulator that provides reference voltage
> +
> +Optional properties:
> +  - spi-max-frequency: SPI maximum frequency
> +
> +Example:
> +
> +adc0: max11100@0 {
> +        compatible = "maxim,max11100";
> +        vref-supply = <&adc0_vref>;
> +        spi-max-frequency = <240000>;
> +};
> +
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 99c0514..a909484 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -285,6 +285,15 @@ config MAX1027
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1027.
>  
> +config MAX11100
> +	tristate "Maxim max11100 ADC driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Maxim max11100 SPI ADC
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max11100.
> +
>  config MAX1363
>  	tristate "Maxim max1363 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 7a40c04..1463044 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
>  obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_MAX1027) += max1027.o
> +obj-$(CONFIG_MAX11100) += max11100.o
>  obj-$(CONFIG_MAX1363) += max1363.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
> diff --git a/drivers/iio/adc/max11100.c b/drivers/iio/adc/max11100.c
> new file mode 100644
> index 0000000..f372ad8
> --- /dev/null
> +++ b/drivers/iio/adc/max11100.c
> @@ -0,0 +1,166 @@
> +/*
> + * iio/adc/max11100.c
> + * Maxim max11100 ADC Driver with IIO interface
> + *
> + * Copyright (C) 2016 Renesas Electronics Corporation
> + * Copyright (C) 2016 Jacopo Mondi
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/driver.h>
> +
> +/*
> + * LSB is the ADC single digital step
> + * 1 LSB = (vref / 2 ^ 16)
> + * AIN = (DIN * LSB)
> + */
> +#define MAX11100_LSB_DIV		(1 << 16)
> +#define MAX11100_LSB(vref) 		(vref / MAX11100_LSB_DIV)
> +
> +struct max11100_state {
> +	const struct max11100_chip_desc *desc;
> +	struct spi_device *spi;
> +	int vref_uv;
> +	struct mutex lock;
> +};
> +
> +static struct iio_chan_spec max11100_channels[] = {
> +	{ /* [0] */
> +		.type = IIO_VOLTAGE,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 16,
> +			.storagebits = 24,
> +			.shift = 8,
> +			.repeat = 1,
> +			.endianness = IIO_BE,
> +		},
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +	},
> +};
> +
> +static struct max11100_chip_desc {
> +	unsigned int num_chan;
> +	const struct iio_chan_spec *channels;
> +} max11100_desc = {
> +	.num_chan = ARRAY_SIZE(max11100_channels),
> +	.channels = max11100_channels,
> +};
> +
> +static int max11100_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	int ret;
> +	struct max11100_state *state = iio_priv(indio_dev);
> +	uint8_t buffer[3];
> +
> +	mutex_lock(&state->lock);
> +
> +	ret = spi_read(state->spi, buffer, sizeof(buffer));
> +	if (ret) {
> +		mutex_unlock(&state->lock);
> +		dev_err(&indio_dev->dev, "SPI transfer failed\n");
> +		return ret;
> +	}
> +	mutex_unlock(&state->lock);
> +
> +	/* the first 8 bits sent out from ADC must be 0s */
> +	if (buffer[0]) {
> +		dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
> +		return -EINVAL;
> +	}
> +
> +	*val = be16_to_cpu(*(uint16_t *)&buffer[1]);
> +	*val = *val * MAX11100_LSB(state->vref_uv) / 1000;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static const struct iio_info max11100_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = max11100_read_raw,
> +};
> +
> +static int max11100_probe(struct spi_device *spi)
> +{
> +	int ret;
> +	struct iio_dev *indio_dev;
> +	struct regulator *vref_reg;
> +	struct max11100_state *state;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	state = iio_priv(indio_dev);
> +	state->spi = spi;
> +	state->desc = &max11100_desc;
> +
> +	mutex_init(&state->lock);
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->info = &max11100_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = state->desc->channels;
> +	indio_dev->num_channels = state->desc->num_chan;
> +
> +	vref_reg = devm_regulator_get(&spi->dev, "vref");
> +	if (IS_ERR(vref_reg))
> +		return PTR_ERR(vref_reg);
> +
> +	ret = regulator_enable(vref_reg);
> +	if (ret)
> +		return ret;
> +
> +	state->vref_uv = regulator_get_voltage(vref_reg);
> +	if (state->vref_uv < 0) {
> +		/* dummy regulator "get_voltage" returns -EINVAL as well */
> +		ret = -EINVAL;
> +		goto disable_regulator;
> +	}
> +
> +	ret = devm_iio_device_register(&spi->dev, indio_dev);
> +	if (ret)
> +		goto disable_regulator;
> +
> +	return 0;
> +
> +disable_regulator:
> +	regulator_disable(vref_reg);
> +	return ret;
> +}
> +
> +static const struct of_device_id max11100_ids[] = {
> +	{.compatible = "maxim,max11100"},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, max11100_ids);
> +
> +static struct spi_driver max11100_driver = {
> +	.driver = {
> +		.name	= "max11100",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = of_match_ptr(max11100_ids),
> +	},
> +	.probe		= max11100_probe,
> +};
> +
> +module_spi_driver(max11100_driver);
> +
> +MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
> +MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
> +MODULE_LICENSE("GPL v2");
>