Re: [PATCH v2 2/2] iio: potentiometer: Add driver for Microchip MCP41xxx/42xxx

[Slawomir Stepien <sst@poczta.fm>]

On lis 14, 2018 09:52, Chris Coffey wrote:
> This patch adds driver support for the Microchip MCP41xxx/42xxx family
> of digital potentiometers:
> 
> DEVICE      Wipers  Positions   Resistance (kOhm)
> MCP41010    1       256         10
> MCP41050    1       256         50
> MCP41100    1       256         100
> MCP42010    2       256         10
> MCP42050    2       256         50
> MCP42100    2       256         100
> 
> Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf

Hi

Some hints inline.

> Signed-off-by: Chris Coffey <cmc@babblebit.net>
> ---
>  drivers/iio/potentiometer/Kconfig    |  12 ++
>  drivers/iio/potentiometer/Makefile   |   1 +
>  drivers/iio/potentiometer/mcp41010.c | 216 +++++++++++++++++++++++++++++++++++
>  3 files changed, 229 insertions(+)
>  create mode 100644 drivers/iio/potentiometer/mcp41010.c
> 
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 79ec2eba49..6303cbe799 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -90,6 +90,18 @@ config MCP4531
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called mcp4531.
>  
> +config MCP41010
> +	tristate "Microchip MCP41xxx/MCP42xxx Digital Potentiometer driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for the Microchip
> +	  MCP41010, MCP41050, MCP41100,
> +	  MCP42010, MCP42050, MCP42100
> +	  digital potentiometer chips.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called mcp41010.
> +
>  config TPL0102
>  	tristate "Texas Instruments digital potentiometer driver"
>  	depends on I2C
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 4af657883c..8ff55138cf 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -11,4 +11,5 @@ obj-$(CONFIG_MAX5487) += max5487.o
>  obj-$(CONFIG_MCP4018) += mcp4018.o
>  obj-$(CONFIG_MCP4131) += mcp4131.o
>  obj-$(CONFIG_MCP4531) += mcp4531.o
> +obj-$(CONFIG_MCP41010) += mcp41010.o
>  obj-$(CONFIG_TPL0102) += tpl0102.o
> diff --git a/drivers/iio/potentiometer/mcp41010.c b/drivers/iio/potentiometer/mcp41010.c
> new file mode 100644
> index 0000000000..19fa50c9ee
> --- /dev/null
> +++ b/drivers/iio/potentiometer/mcp41010.c
> @@ -0,0 +1,216 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Industrial I/O driver for Microchip digital potentiometers
> + *
> + * Copyright (c) 2018 Chris Coffey <cmc@babblebit.net>
> + * Based on: Slawomir Stepien's code from mcp4131.c
> + *
> + * Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf
> + *
> + * DEVID	#Wipers	#Positions	Resistance (kOhm)
> + * mcp41010	1	256		10
> + * mcp41050	1	256		50
> + * mcp41100	1	256		100
> + * mcp42010	2	256		10
> + * mcp42050	2	256		50
> + * mcp42100	2	256		100
> + */
> +
> +#include <linux/cache.h>
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/types.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +
> +#define MCP41010_MAX_WIPERS	2
> +#define MCP41010_WRITE		BIT(4)
> +#define MCP41010_WIPER_MAX	255
> +#define MCP41010_WIPER_CHANNEL	BIT(0)
> +
> +struct mcp41010_cfg {
> +	int wipers;
> +	int kohms;
> +};
> +
> +enum mcp41010_type {
> +	MCP41010,
> +	MCP41050,
> +	MCP41100,
> +	MCP42010,
> +	MCP42050,
> +	MCP42100,
> +};
> +
> +static const struct mcp41010_cfg mcp41010_cfg[] = {
> +	[MCP41010] = { .wipers = 1, .kohms =  10, },
> +	[MCP41050] = { .wipers = 1, .kohms =  50, },
> +	[MCP41100] = { .wipers = 1, .kohms = 100, },
> +	[MCP42010] = { .wipers = 2, .kohms =  10, },
> +	[MCP42050] = { .wipers = 2, .kohms =  50, },
> +	[MCP42100] = { .wipers = 2, .kohms = 100, },
> +};
> +
> +struct mcp41010_data {
> +	struct spi_device *spi;
> +	const struct mcp41010_cfg *cfg;
> +	struct mutex lock; /* Protect write sequences */
> +	unsigned int value[MCP41010_MAX_WIPERS]; /* Cache wiper values */
> +	u8 buf[2] ____cacheline_aligned;
> +};
> +
> +#define MCP41010_CHANNEL(ch) {					\
> +	.type = IIO_RESISTANCE,					\
> +	.indexed = 1,						\
> +	.output = 1,						\
> +	.channel = (ch),					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +}
> +
> +static const struct iio_chan_spec mcp41010_channels[] = {
> +	MCP41010_CHANNEL(0),
> +	MCP41010_CHANNEL(1),
> +};
> +
> +static int mcp41010_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct mcp41010_data *data = iio_priv(indio_dev);
> +	int channel = chan->channel;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = data->value[channel];
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1000 * data->cfg->kohms;
> +		*val2 = MCP41010_WIPER_MAX;
> +		return IIO_VAL_FRACTIONAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int mcp41010_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	int err;
> +	struct mcp41010_data *data = iio_priv(indio_dev);
> +	int channel = chan->channel;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val > MCP41010_WIPER_MAX || val < 0)
> +			return -EINVAL;
> +		break;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&data->lock);
> +
> +	data->buf[0] = MCP41010_WIPER_CHANNEL << channel;
> +	data->buf[0] |= MCP41010_WRITE;
> +	data->buf[1] = val & 0xff;
> +
> +	err = spi_write(data->spi, data->buf, 2);
> +	if (!err)
> +		data->value[channel] = val;
> +
> +	mutex_unlock(&data->lock);
> +
> +	return err;
> +}
> +
> +static const struct iio_info mcp41010_info = {
> +	.read_raw = mcp41010_read_raw,
> +	.write_raw = mcp41010_write_raw,
> +};
> +
> +static int mcp41010_probe(struct spi_device *spi)
> +{
> +	int err;
> +	struct device *dev = &spi->dev;
> +	unsigned long devid = spi_get_device_id(spi)->driver_data;

I guess the calculation of devid value can now be done only when
of_device_get_match_data() did not return config.

> +	struct mcp41010_data *data;
> +	struct iio_dev *indio_dev;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	spi_set_drvdata(spi, indio_dev);
> +	data->spi = spi;
> +	data->cfg = of_device_get_match_data(&spi->dev);
> +	if (!data->cfg)
> +		data->cfg = &mcp41010_cfg[devid];
> +
> +	mutex_init(&data->lock);
> +
> +	indio_dev->dev.parent = dev;
> +	indio_dev->info = &mcp41010_info;
> +	indio_dev->channels = mcp41010_channels;
> +	indio_dev->num_channels = data->cfg->wipers;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +
> +	err = devm_iio_device_register(dev, indio_dev);
> +	if (err) {
> +		dev_info(&spi->dev, "Unable to register %s\n", indio_dev->name);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id mcp41010_match[] = {
> +	{ .compatible = "microchip,mcp41010",
> +		.data = &mcp41010_cfg[MCP41010] },
> +	{ .compatible = "microchip,mcp41050",
> +		.data = &mcp41010_cfg[MCP41050] },
> +	{ .compatible = "microchip,mcp41100",
> +		.data = &mcp41010_cfg[MCP41100] },
> +	{ .compatible = "microchip,mcp42010",
> +		.data = &mcp41010_cfg[MCP42010] },
> +	{ .compatible = "microchip,mcp42050",
> +		.data = &mcp41010_cfg[MCP42050] },
> +	{ .compatible = "microchip,mcp42100",
> +		.data = &mcp41010_cfg[MCP42100] },

It looks that you can fit these into 80 chars column.

> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mcp41010_match);
> +
> +static const struct spi_device_id mcp41010_id[] = {
> +	{ "mcp41010", MCP41010 },
> +	{ "mcp41050", MCP41050 },
> +	{ "mcp41100", MCP41100 },
> +	{ "mcp42010", MCP42010 },
> +	{ "mcp42050", MCP42050 },
> +	{ "mcp42100", MCP42100 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, mcp41010_id);
> +
> +static struct spi_driver mcp41010_driver = {
> +	.driver = {
> +		.name	= "mcp41010",
> +		.of_match_table = mcp41010_match,
> +	},
> +	.probe		= mcp41010_probe,
> +	.id_table	= mcp41010_id,
> +};
> +
> +module_spi_driver(mcp41010_driver);
> +
> +MODULE_AUTHOR("Chris Coffey <cmc@babblebit.net>");
> +MODULE_DESCRIPTION("MCP41010 digital potentiometer");
> +MODULE_LICENSE("GPL v2");

-- 
Slawomir Stepien