Re: [PATCH 1/3] iio: amplifiers: hmc425a: Add support for HMC425A step attenuator with gpio interface

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Mon, 2020-01-13 at 16:15 +0200, Beniamin Bia wrote:
> From: Michael Hennerich <michael.hennerich@analog.com>
> 
> This patch adds support for the HMC425A 0.5 dB LSB GaAs MMIC 6-BIT
> DIGITAL POSITIVE CONTROL ATTENUATOR, 2.2 - 8.0 GHz.
> 
> Datasheet:
> https://www.analog.com/media/en/technical-documentation/data-sheets/hmc425A.pdf
> 
> Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> Signed-off-by: Beniamin Bia <beniamin.bia@analog.com>
> ---
>  drivers/iio/amplifiers/Kconfig   |  10 ++
>  drivers/iio/amplifiers/Makefile  |   1 +
>  drivers/iio/amplifiers/hmc425a.c | 247 +++++++++++++++++++++++++++++++
>  3 files changed, 258 insertions(+)
>  create mode 100644 drivers/iio/amplifiers/hmc425a.c
> 
> diff --git a/drivers/iio/amplifiers/Kconfig
> b/drivers/iio/amplifiers/Kconfig
> index da7f126d197b..9b02c9a2bc8a 100644
> --- a/drivers/iio/amplifiers/Kconfig
> +++ b/drivers/iio/amplifiers/Kconfig
> @@ -22,4 +22,14 @@ config AD8366
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad8366.
>  
> +config HMC425
> +	tristate "Analog Devices HMC425A and similar GPIO Gain Amplifiers"
> +	depends on GPIOLIB
> +	help
> +	  Say yes here to build support for Analog Devices HMC425A and
> similar
> +	  gain amplifiers or step attenuators.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called hmc425a.
> +
>  endmenu
> diff --git a/drivers/iio/amplifiers/Makefile
> b/drivers/iio/amplifiers/Makefile
> index 9abef2ebe9bc..19a89db1d9b1 100644
> --- a/drivers/iio/amplifiers/Makefile
> +++ b/drivers/iio/amplifiers/Makefile
> @@ -5,3 +5,4 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_AD8366) += ad8366.o
> +obj-$(CONFIG_HMC425) += hmc425a.o
> \ No newline at end of file
> diff --git a/drivers/iio/amplifiers/hmc425a.c
> b/drivers/iio/amplifiers/hmc425a.c
> new file mode 100644
> index 000000000000..525ebadaf1e8
> --- /dev/null
> +++ b/drivers/iio/amplifiers/hmc425a.c
> @@ -0,0 +1,247 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * HMC425A and similar Gain Amplifiers
> + *
> + * Copyright 2020 Analog Devices Inc.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/sysfs.h>
> +
> +enum hmc425a_type {
> +	ID_HMC425A,
> +};
> +
> +struct hmc425a_chip_info {
> +	const struct iio_chan_spec	*channels;
> +	unsigned int			num_channels;
> +	unsigned int			num_gpios;
> +	int				gain_min;
> +	int				gain_max;
> +	int				default_gain;
> +};
> +
> +struct hmc425a_state {
> +	struct	regulator *reg;
> +	struct	mutex lock; /* protect sensor state */
> +	struct	hmc425a_chip_info *chip_info;
> +	struct	gpio_descs *gpios;
> +	enum	hmc425a_type type;
> +	u32	gain;
> +};
> +
> +static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
> +{
> +	struct hmc425a_state *st = iio_priv(indio_dev);
> +	int i, *values;
> +
> +	values = kmalloc_array(st->chip_info->num_gpios, sizeof(int),
> +			       GFP_KERNEL);
> +	if (!values)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < st->chip_info->num_gpios; i++)
> +		values[i] = (value >> i) & 1;
> +
> +	gpiod_set_array_value_cansleep(st->gpios->ndescs, st->gpios->desc,
> +				       values);
> +	kfree(values);

I think this may be an older variant of the driver.
The 'values' array could be static with a max value.

And the return value of gpiod_set_array_value_cansleep() could be returned
from this function.

> +	return 0;
> +}
> +
> +static int hmc425a_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan, int *val,
> +			    int *val2, long m)
> +{
> +	struct hmc425a_state *st = iio_priv(indio_dev);
> +	int code, gain = 0;
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	switch (m) {
> +	case IIO_CHAN_INFO_HARDWAREGAIN:
> +		code = st->gain;
> +
> +		switch (st->type) {
> +		case ID_HMC425A:
> +			gain = ~code * -500;
> +			break;
> +		}
> +
> +		/* Values in dB */
> +		*val = gain / 1000;
> +		*val2 = (gain % 1000) * 1000;
> +
> +		ret = IIO_VAL_INT_PLUS_MICRO_DB;
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +};
> +
> +static int hmc425a_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan, int val,
> +			     int val2, long mask)
> +{
> +	struct hmc425a_state *st = iio_priv(indio_dev);
> +	struct hmc425a_chip_info *inf = st->chip_info;
> +	int code = 0, gain;
> +	int ret;
> +
> +	/* Values in dB */
> +	if (val < 0)
> +		gain = (val * 1000) - (val2 / 1000);
> +	else
> +		gain = (val * 1000) + (val2 / 1000);
> +
> +	if (gain > inf->gain_max || gain < inf->gain_min)
> +		return -EINVAL;
> +
> +	switch (st->type) {
> +	case ID_HMC425A:
> +		code = ~((abs(gain) / 500) & 0x3F);
> +		break;
> +	}
> +
> +	mutex_lock(&st->lock);
> +	switch (mask) {
> +	case IIO_CHAN_INFO_HARDWAREGAIN:
> +		st->gain = code;
> +
> +		ret = hmc425a_write(indio_dev, st->gain);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static const struct iio_info hmc425a_info = {
> +	.read_raw = &hmc425a_read_raw,
> +	.write_raw = &hmc425a_write_raw,
> +};
> +
> +#define
> HMC425A_CHAN(_channel)                                          \
> +{                                                                      \
> +	.type = IIO_VOLTAGE, .output = 1, .indexed = 1,                \
> +	.channel = _channel,                                           \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),         \
> +}
> +
> +static const struct iio_chan_spec hmc425a_channels[] = {
> +	HMC425A_CHAN(0),
> +};
> +
> +/* Match table for of_platform binding */
> +static const struct of_device_id hmc425a_of_match[] = {
> +	{ .compatible = "adi,hmc425a", .data = (void *)ID_HMC425A },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, hmc425a_of_match);
> +
> +static void hmc425a_remove(void *data)
> +{
> +	struct hmc425a_state *st = data;
> +
> +	regulator_disable(st->reg);
> +}
> +
> +static struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
> +	[ID_HMC425A] = {
> +		.channels = hmc425a_channels,
> +		.num_channels = ARRAY_SIZE(hmc425a_channels),
> +		.num_gpios = 6,
> +		.gain_min = -31500,
> +		.gain_max = 0,
> +		.default_gain = -0x40, /* set default gain -31.5db*/
> +	},
> +};
> +
> +static int hmc425a_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	const struct of_device_id *id;
> +	struct iio_dev *indio_dev;
> +	struct hmc425a_state *st;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	id = of_match_device(hmc425a_of_match, &pdev->dev);
> +	if (!id)
> +		ret = -ENODEV;
> +
> +	st->type = (enum hmc425a_type)id->data;
> +
> +	st->chip_info = &hmc425a_chip_info_tbl[st->type];
> +	indio_dev->num_channels = st->chip_info->num_channels;
> +	indio_dev->channels = st->chip_info->channels;
> +	st->gain = st->chip_info->default_gain;
> +
> +	st->gpios = devm_gpiod_get_array(&pdev->dev, "ctrl",
> GPIOD_OUT_LOW);
> +	if (IS_ERR(st->gpios)) {
> +		ret = PTR_ERR(st->gpios);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "failed to get gpios\n");
> +		return ret;
> +	}
> +
> +	if (st->gpios->ndescs != st->chip_info->num_gpios) {
> +		dev_err(&pdev->dev, "%d GPIOs needed to operate\n",
> +			st->chip_info->num_gpios);
> +		return -ENODEV;
> +	}
> +
> +	st->reg = devm_regulator_get(&pdev->dev, "vcc");
> +	if (!IS_ERR(st->reg)) {
> +		ret = regulator_enable(st->reg);
> +		if (ret)
> +			return ret;
> +		ret = devm_add_action_or_reset(&pdev->dev, hmc425a_remove,
> st);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +	mutex_init(&st->lock);
> +
> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->name = np->name;
> +	indio_dev->info = &hmc425a_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	return devm_iio_device_register(&pdev->dev, indio_dev);
> +}
> +
> +static struct platform_driver hmc425a_driver = {
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +		.of_match_table = hmc425a_of_match,
> +	},
> +	.probe = hmc425a_probe,
> +};
> +module_platform_driver(hmc425a_driver);
> +
> +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
> +MODULE_DESCRIPTION(
> +	"Analog Devices HMC425A and similar GPIO control Gain Amplifiers");
> +MODULE_LICENSE("GPL v2");