Re: [PATCH v4] iio: max5481: Add support for Maxim digital potentiometers

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

On 26/01/17 20:26, Slawomir Stepien wrote:
> From: Matt Weber <matthew.weber-lFk7bPDcGtkY5TsXZYaR1UEOCMrvLtNR@public.gmane.org>
> 
> Add implementation for Maxim Integrated 5481, 5482, 5483,
> and 5484 digital potentiometer devices.
> 
> Datasheet:
> http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
> 
> Signed-off-by: Maury Anderson <maury.anderson-lFk7bPDcGtkY5TsXZYaR1UEOCMrvLtNR@public.gmane.org>
> Signed-off-by: Matthew Weber <matthew.weber-lFk7bPDcGtkY5TsXZYaR1UEOCMrvLtNR@public.gmane.org>
> Signed-off-by: Slawomir Stepien <sst-IjDXvh/HVVUAvxtiuMwx3w@public.gmane.org>
> Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Looks good to me.

Applied to the togreg branch of iio.git - initially pushed out as
testing for the magic autobuilders to play with it.

Thanks for picking this one up and running with it,

Jonathan
> ---
> 
> This is my resubmission of this patch after original authors decided not to
> pursuit it inclusion into kernel.
> 
> Tested using signal analyzer.
> 
> Changes since v3:
> * spi_writes are now using literals for size parameter 
> * using of_match_device to get the of data pointer if matched
> * Add Acked-by
> 
> Changes since v2:
> * spi write buffer moved to struct max5481_data and ____cacheline_aligned.
> * max5481_write_cmd now uses pointer to struct max5481_data as a first argument.
> 
> Changes since v1:
> * removed not needed '``' and 'c' chars
> * includes are now sorted
> * added coma to last item in enum max5481_variant
> * removed maxpos from struct max5481_cfg
> * max5481_CHANNEL is no MAX5481_CHANNEL and it does not have 'ch' argument
> * max5481_write_cmd is now based around switch
> * removed not needed cast in max5481_write_cmd
> * wpier state is saved after iio_device_unregister
> * changed names in spi_device_id and acpi_device_id to be equal to names in
> * of_device_id
> 
> ---
>  .../bindings/iio/potentiometer/max5481.txt         |  23 +++
>  drivers/iio/potentiometer/Kconfig                  |  11 +
>  drivers/iio/potentiometer/Makefile                 |   1 +
>  drivers/iio/potentiometer/max5481.c                | 223 +++++++++++++++++++++
>  4 files changed, 258 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/max5481.txt
>  create mode 100644 drivers/iio/potentiometer/max5481.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/max5481.txt b/Documentation/devicetree/bindings/iio/potentiometer/max5481.txt
> new file mode 100644
> index 000000000000..6a91b106e076
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/max5481.txt
> @@ -0,0 +1,23 @@
> +* Maxim Linear-Taper Digital Potentiometer MAX5481-MAX5484
> +
> +The node for this driver must be a child node of a SPI controller, hence
> +all mandatory properties described in
> +
> +        Documentation/devicetree/bindings/spi/spi-bus.txt
> +
> +must be specified.
> +
> +Required properties:
> +	- compatible:  	Must be one of the following, depending on the
> +			model:
> +			"maxim,max5481"
> +			"maxim,max5482"
> +			"maxim,max5483"
> +			"maxim,max5484"
> +
> +Example:
> +max548x: max548x@0 {
> +	compatible = "maxim,max5482";
> +	spi-max-frequency = <7000000>;
> +	reg = <0>; /* chip-select */
> +};
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 2e9da1cf3297..8bf282510be6 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -15,6 +15,17 @@ config DS1803
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ds1803.
>  
> +config MAX5481
> +        tristate "Maxim MAX5481-MAX5484 Digital Potentiometer driver"
> +        depends on SPI
> +        help
> +          Say yes here to build support for the Maxim
> +          MAX5481, MAX5482, MAX5483, MAX5484 digital potentiometer
> +          chips.
> +
> +          To compile this driver as a module, choose M here: the
> +          module will be called max5481.
> +
>  config MAX5487
>          tristate "Maxim MAX5487/MAX5488/MAX5489 Digital Potentiometer driver"
>          depends on SPI
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 8adb58f38c0b..2260d40e0936 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -4,6 +4,7 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_DS1803) += ds1803.o
> +obj-$(CONFIG_MAX5481) += max5481.o
>  obj-$(CONFIG_MAX5487) += max5487.o
>  obj-$(CONFIG_MCP4131) += mcp4131.o
>  obj-$(CONFIG_MCP4531) += mcp4531.o
> diff --git a/drivers/iio/potentiometer/max5481.c b/drivers/iio/potentiometer/max5481.c
> new file mode 100644
> index 000000000000..926554991244
> --- /dev/null
> +++ b/drivers/iio/potentiometer/max5481.c
> @@ -0,0 +1,223 @@
> +/*
> + * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver
> + * Copyright 2016 Rockwell Collins
> + *
> + * Datasheet:
> + * http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
> + *
> + * 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/acpi.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +
> +/* write wiper reg */
> +#define MAX5481_WRITE_WIPER (0 << 4)
> +/* copy wiper reg to NV reg */
> +#define MAX5481_COPY_AB_TO_NV (2 << 4)
> +/* copy NV reg to wiper reg */
> +#define MAX5481_COPY_NV_TO_AB (3 << 4)
> +
> +#define MAX5481_MAX_POS    1023
> +
> +enum max5481_variant {
> +	max5481,
> +	max5482,
> +	max5483,
> +	max5484,
> +};
> +
> +struct max5481_cfg {
> +	int kohms;
> +};
> +
> +static const struct max5481_cfg max5481_cfg[] = {
> +	[max5481] = { .kohms =  10, },
> +	[max5482] = { .kohms =  50, },
> +	[max5483] = { .kohms =  10, },
> +	[max5484] = { .kohms =  50, },
> +};
> +
> +struct max5481_data {
> +	struct spi_device *spi;
> +	const struct max5481_cfg *cfg;
> +	u8 msg[3] ____cacheline_aligned;
> +};
> +
> +#define MAX5481_CHANNEL {					\
> +	.type = IIO_RESISTANCE,					\
> +	.indexed = 1,						\
> +	.output = 1,						\
> +	.channel = 0,						\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +}
> +
> +static const struct iio_chan_spec max5481_channels[] = {
> +	MAX5481_CHANNEL,
> +};
> +
> +static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val)
> +{
> +	struct spi_device *spi = data->spi;
> +
> +	data->msg[0] = cmd;
> +
> +	switch (cmd) {
> +	case MAX5481_WRITE_WIPER:
> +		data->msg[1] = val >> 2;
> +		data->msg[2] = (val & 0x3) << 6;
> +		return spi_write(spi, data->msg, 3);
> +
> +	case MAX5481_COPY_AB_TO_NV:
> +	case MAX5481_COPY_NV_TO_AB:
> +		return spi_write(spi, data->msg, 1);
> +
> +	default:
> +		return -EIO;
> +	}
> +}
> +
> +static int max5481_read_raw(struct iio_dev *indio_dev,
> +		struct iio_chan_spec const *chan,
> +		int *val, int *val2, long mask)
> +{
> +	struct max5481_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_SCALE)
> +		return -EINVAL;
> +
> +	*val = 1000 * data->cfg->kohms;
> +	*val2 = MAX5481_MAX_POS;
> +
> +	return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max5481_write_raw(struct iio_dev *indio_dev,
> +		struct iio_chan_spec const *chan,
> +		int val, int val2, long mask)
> +{
> +	struct max5481_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	if (val < 0 || val > MAX5481_MAX_POS)
> +		return -EINVAL;
> +
> +	return max5481_write_cmd(data, MAX5481_WRITE_WIPER, val);
> +}
> +
> +static const struct iio_info max5481_info = {
> +	.read_raw = max5481_read_raw,
> +	.write_raw = max5481_write_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +#if defined(CONFIG_OF)
> +static const struct of_device_id max5481_match[] = {
> +	{ .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] },
> +	{ .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] },
> +	{ .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] },
> +	{ .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, max5481_match);
> +#endif
> +
> +static int max5481_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct max5481_data *data;
> +	const struct spi_device_id *id = spi_get_device_id(spi);
> +	const struct of_device_id *match;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(&spi->dev, indio_dev);
> +	data = iio_priv(indio_dev);
> +
> +	data->spi = spi;
> +
> +	match = of_match_device(of_match_ptr(max5481_match), &spi->dev);
> +	if (match)
> +		data->cfg = of_device_get_match_data(&spi->dev);
> +	else
> +		data->cfg = &max5481_cfg[id->driver_data];
> +
> +	indio_dev->name = id->name;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	/* variant specific configuration */
> +	indio_dev->info = &max5481_info;
> +	indio_dev->channels = max5481_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max5481_channels);
> +
> +	/* restore wiper from NV */
> +	ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	return iio_device_register(indio_dev);
> +}
> +
> +static int max5481_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
> +	struct max5481_data *data = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	/* save wiper reg to NV reg */
> +	return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
> +}
> +
> +static const struct spi_device_id max5481_id_table[] = {
> +	{ "max5481", max5481 },
> +	{ "max5482", max5482 },
> +	{ "max5483", max5483 },
> +	{ "max5484", max5484 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, max5481_id_table);
> +
> +#if defined(CONFIG_ACPI)
> +static const struct acpi_device_id max5481_acpi_match[] = {
> +	{ "max5481", max5481 },
> +	{ "max5482", max5482 },
> +	{ "max5483", max5483 },
> +	{ "max5484", max5484 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, max5481_acpi_match);
> +#endif
> +
> +static struct spi_driver max5481_driver = {
> +	.driver = {
> +		.name  = "max5481",
> +		.owner = THIS_MODULE,
> +		.of_match_table = of_match_ptr(max5481_match),
> +		.acpi_match_table = ACPI_PTR(max5481_acpi_match),
> +	},
> +	.probe = max5481_probe,
> +	.remove = max5481_remove,
> +	.id_table = max5481_id_table,
> +};
> +
> +module_spi_driver(max5481_driver);
> +
> +MODULE_AUTHOR("Maury Anderson <maury.anderson-lFk7bPDcGtkY5TsXZYaR1UEOCMrvLtNR@public.gmane.org>");
> +MODULE_DESCRIPTION("max5481 SPI driver");
> +MODULE_LICENSE("GPL v2");
> 

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