Re: [PATCH v3 2/2] iio: ad5272: Add support for Analog Devices digital potentiometers

[Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Wed, 17 Jan 2018 11:38:28 +0800
Phil Reid <preid-qgqNFa1JUf/o2iN0hyhwsIdd74u8MsAO@public.gmane.org> wrote:

> Add implementation for Analog Devices AD5272 and AD5274 digital
> potentiometer devices.
> 
> Signed-off-by: Phil Reid <preid-qgqNFa1JUf/o2iN0hyhwsIdd74u8MsAO@public.gmane.org>
A couple more minor comments.

Jonathan

> ---
>  drivers/iio/potentiometer/Kconfig  |  10 ++
>  drivers/iio/potentiometer/Makefile |   1 +
>  drivers/iio/potentiometer/ad5272.c | 231 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 242 insertions(+)
>  create mode 100644 drivers/iio/potentiometer/ad5272.c
> 
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 8bf2825..0b04063 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -5,6 +5,16 @@
>  
>  menu "Digital potentiometers"
>  
> +config AD5272
> +	tristate "Analog Devices AD5272 Digital Potentiometer driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for the Analog Devices AD5272
> +	  digital potentiometer chip.

You need to list he compatible parts here so that people looking for
the driver can find it.  Usually the short text states 'and similar'
and the help text contains a list of parts.  AD5274 is missing here.

> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad5272.
> +
>  config DS1803
>  	tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
>  	depends on I2C
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 2260d40..498bbb8 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -3,6 +3,7 @@
>  #
>  
>  # When adding new entries keep the list in alphabetical order
> +obj-$(CONFIG_AD5272) += ad5272.o
>  obj-$(CONFIG_DS1803) += ds1803.o
>  obj-$(CONFIG_MAX5481) += max5481.o
>  obj-$(CONFIG_MAX5487) += max5487.o
> diff --git a/drivers/iio/potentiometer/ad5272.c b/drivers/iio/potentiometer/ad5272.c
> new file mode 100644
> index 0000000..b40f111
> --- /dev/null
> +++ b/drivers/iio/potentiometer/ad5272.c
> @@ -0,0 +1,231 @@
> +/*
> + * Analog Devices AD5372 digital potentiometer driver
> + * Copyright (C) 2018 Phil Reid <preid-qgqNFa1JUf/o2iN0hyhwsIdd74u8MsAO@public.gmane.org>
> + *
> + * Datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/AD5272_5274.pdf
> + *
> + * DEVID	#Wipers	#Positions	Resistor Opts (kOhm)	i2c address
> + * ad5272	1	1024		20, 50, 100		01011xx
> + * ad5274	1	256		20, 100			01011xx
> + *
> + * SPDX-License-Identifier: GPL-2.0+
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +
> +#define  AD5272_RDAC_WR  1
> +#define  AD5272_RDAC_RD  2
> +#define  AD5272_RESET    4
> +#define  AD5272_CTL      7
> +
> +#define  AD5272_RDAC_WR_EN  BIT(1)
> +
> +struct ad5272_cfg {
> +	int max_pos;
> +	int kohms;
> +	int shift;
> +};
> +
> +enum ad5272_type {
> +	AD5272_020,
> +	AD5272_050,
> +	AD5272_100,
> +	AD5274_020,
> +	AD5274_100,
> +};
> +
> +static const struct ad5272_cfg ad5272_cfg[] = {
> +	[AD5272_020] = { .max_pos = 1024, .kohms = 20 },
> +	[AD5272_050] = { .max_pos = 1024, .kohms = 50 },
> +	[AD5272_100] = { .max_pos = 1024, .kohms = 100 },
> +	[AD5274_020] = { .max_pos = 256,  .kohms = 20,  .shift = 2 },
> +	[AD5274_100] = { .max_pos = 256,  .kohms = 100, .shift = 2 },
> +};
> +
> +struct ad5272_data {
> +	struct i2c_client       *client;
> +	struct mutex            lock;
> +	const struct ad5272_cfg *cfg;
> +	u8                      buf[2] ____cacheline_aligned;
> +};
> +
> +static const struct iio_chan_spec ad5272_channel = {
> +	.type = IIO_RESISTANCE,
> +	.output = 1,
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +};
> +
> +static int ad5272_write(struct ad5272_data *data, int reg, int val)
> +{
> +	int ret;
> +
> +	data->buf[0] = (reg << 2) | ((val >> 8) & 0x3);
> +	data->buf[1] = (u8)val;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
> +	mutex_unlock(&data->lock);
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static int ad5272_read(struct ad5272_data *data, int reg, int *val)
> +{
> +	int ret;
> +
> +	data->buf[0] = reg << 2;
> +	data->buf[1] = 0;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
> +	if (ret < 0)
> +		goto error;
> +
> +	ret = i2c_master_recv(data->client, data->buf, sizeof(data->buf));
> +	if (ret < 0)
> +		goto error;
> +
> +	*val = ((data->buf[0] & 0x3) << 8) | data->buf[1];
> +	ret = 0;
> +error:
> +	mutex_unlock(&data->lock);
> +	return ret;
> +}
> +
> +static int ad5272_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	struct ad5272_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW: {
> +		ret = ad5272_read(data, AD5272_RDAC_RD, val);
> +		*val = *val >> data->cfg->shift;
> +		return ret ? ret : IIO_VAL_INT;
> +	}
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1000 * data->cfg->kohms;
> +		*val2 = data->cfg->max_pos;
> +		return IIO_VAL_FRACTIONAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad5272_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	struct ad5272_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	if (val >= data->cfg->max_pos || val < 0 || val2)
> +		return -EINVAL;
> +
> +	return ad5272_write(data, AD5272_RDAC_WR, val << data->cfg->shift);
> +}
> +
> +static const struct iio_info ad5272_info = {
> +	.read_raw = ad5272_read_raw,
> +	.write_raw = ad5272_write_raw,
> +};
> +
> +static int ad5272_reset(struct ad5272_data *data)
> +{
> +	struct gpio_desc *reset_gpio;
> +
> +	reset_gpio = devm_gpiod_get_optional(&data->client->dev, "reset",
> +		GPIOD_OUT_LOW);
> +	if (IS_ERR(reset_gpio))
> +		return PTR_ERR(reset_gpio);
> +
> +	if (reset_gpio) {
> +		udelay(1);
> +		gpiod_set_value(reset_gpio, 1);
> +	} else {
> +		ad5272_write(data, AD5272_RESET, 0);
> +	}
> +	usleep_range(1000, 2000);
kernel coding conventions (and readability) put a blank line
before return statements.

> +	return 0;
> +}
> +
> +static int ad5272_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct iio_dev *indio_dev;
> +	struct ad5272_data *data;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +	mutex_init(&data->lock);
> +	data->cfg = &ad5272_cfg[id->driver_data];
> +
> +	ret = ad5272_reset(data);
> +	if (ret)
> +		return ret;
> +
> +	ret = ad5272_write(data, AD5272_CTL, AD5272_RDAC_WR_EN);
> +	if (ret < 0)
> +		return -ENODEV;
> +
> +	indio_dev->dev.parent = dev;
> +	indio_dev->info = &ad5272_info;
> +	indio_dev->channels = &ad5272_channel;
> +	indio_dev->num_channels = 1;
> +	indio_dev->name = client->name;
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +#if defined(CONFIG_OF)
> +static const struct of_device_id ad5272_dt_ids[] = {
> +	{ .compatible = "adi,ad5272-020", .data = (void *)AD5272_020 },
> +	{ .compatible = "adi,ad5272-050", .data = (void *)AD5272_050 },
> +	{ .compatible = "adi,ad5272-100", .data = (void *)AD5272_100 },
> +	{ .compatible = "adi,ad5274-020", .data = (void *)AD5274_020 },
> +	{ .compatible = "adi,ad5274-100", .data = (void *)AD5274_100 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, ad5272_dt_ids);
> +#endif /* CONFIG_OF */
> +
> +static const struct i2c_device_id ad5272_id[] = {
> +	{ "ad5272-020", AD5272_020 },
> +	{ "ad5272-050", AD5272_050 },
> +	{ "ad5272-100", AD5272_100 },
> +	{ "ad5274-020", AD5274_020 },
> +	{ "ad5274-100", AD5274_100 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ad5272_id);
> +
> +static struct i2c_driver ad5272_driver = {
> +	.driver = {
> +		.name	= "ad5272",
> +		.of_match_table = of_match_ptr(ad5272_dt_ids),
> +	},
> +	.probe		= ad5272_probe,
> +	.id_table	= ad5272_id,
> +};
> +
> +module_i2c_driver(ad5272_driver);
> +
> +MODULE_AUTHOR("Phil Reid <preid-TeWIRZsGUAnP+dxuUfoltA@public.gmane.org>");
> +MODULE_DESCRIPTION("AD5272 digital potentiometer");
> +MODULE_LICENSE("GPL v2");

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