Re: [PATCH 5/5] staging: drivers: iio: adc: Adc MAX77541 ADC Support

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 7 Dec 2022 12:08:44 +0300
Okan Sahin <okan.sahin@analog.com> wrote:

> This patch add adc support for MAX77541.
> 
> The MAX77541 has an 8-bit Successive Approximation Register (SAR) ADC
> with four multiplexers for supporting the telemetry feature

Good to add a little detail on what features the driver currently supports.

> 
> Signed-off-by: Okan Sahin <okan.sahin@analog.com>

...

> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 791612ca6012..2e7833b33f12 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -696,6 +696,17 @@ config MAX1363
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1363.
>  
> +config MAX77541_ADC
> +	tristate "Analog Devices MAX77541 ADC driver"
> +	depends on MFD_MAX77541
> +	help
> +	  This driver controls a Analog Devices MAX77541 adc
ADC

> +	  via I2C bus. This device has one adc. Say yes here to build
> +	  support for Analog Devices MAX77541 ADC interface.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max77541-adc.
> +

...

> diff --git a/drivers/iio/adc/max77541-adc.c b/drivers/iio/adc/max77541-adc.c
> new file mode 100644
> index 000000000000..7ca8576bd4e1
> --- /dev/null
> +++ b/drivers/iio/adc/max77541-adc.c
> @@ -0,0 +1,224 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2022 Analog Devices, Inc.
> + * ADI MAX77541 ADC Driver with IIO interface
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/iio/iio.h>
> +#include <include/linux/mfd/max77541.h>

Move this driver specific header include to below the main
block. We want to make it clear it is special.

> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/driver.h>
> +#include <linux/regulator/of_regulator.h>

Would be very very surprised to see off_regulator.h correctly included
in an IIO driver.  Check all of these for whether they are necessary
(rather than cut and paste from another driver).

> +
> +#define MAX77541_ADC_CHANNEL(_channel, _name, _type, _reg) \
> +	{							\
> +		.type = _type,					\
> +		.indexed = 1,					\
> +		.channel = _channel,				\
> +		.address = _reg,				\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
> +				      BIT(IIO_CHAN_INFO_SCALE) |\
> +				      BIT(IIO_CHAN_INFO_OFFSET),\
> +		.datasheet_name = _name,			\
> +	}
> +
> +enum {
> +	MAX77541_ADC_CH1_I = 0,
> +	MAX77541_ADC_CH2_I,
> +	MAX77541_ADC_CH3_I,
> +	MAX77541_ADC_CH6_I,
> +
> +	MAX77541_ADC_IRQMAX_I,
> +};
> +
> +struct max77541_adc_iio {
> +	struct regmap	*regmap;
> +	int irq;
> +	int irq_arr[MAX77541_ADC_IRQMAX_I];

Clear out unused elements until the follow up patch that actually makes
us of them. For now they are just distracting noise.

> +};
> +
> +enum max77541_adc_channel {
> +	MAX77541_ADC_VSYS_V = 0,
> +	MAX77541_ADC_VOUT1_V,
> +	MAX77541_ADC_VOUT2_V,
> +	MAX77541_ADC_TEMP,
> +};
> +
> +static int max77541_adc_offset(struct iio_dev *indio_dev,
> +			       struct iio_chan_spec const *chan,
> +			       int *val, int *val2)
> +{
> +	switch (chan->channel) {
> +	case MAX77541_ADC_VSYS_V:
> +	case MAX77541_ADC_VOUT1_V:
> +	case MAX77541_ADC_VOUT2_V:
> +		*val = 0;
> +		*val2 = 0;
> +		return IIO_VAL_INT_PLUS_MICRO;

If the offset is zero, then don't have the interface.  Default
assumption if OFFSET is not provided is that the offset is 0.


> +	case MAX77541_ADC_TEMP:
> +		*val = -273;
> +		*val2 = 0;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int max77541_adc_scale(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan,
> +			      int *val, int *val2)
> +{
> +	struct max77541_adc_iio *info = iio_priv(indio_dev);
> +	unsigned int reg_val;
> +	int ret;
> +
> +	switch (chan->channel) {
> +	case MAX77541_ADC_VSYS_V:
> +		*val = 0;
> +		*val2 = 25000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case MAX77541_ADC_VOUT1_V:
> +		ret = regmap_read(info->regmap, MAX77541_REG_M2_CFG1, &reg_val);
> +		if (ret)
> +			return ret;
> +
> +		reg_val = FIELD_GET(MAX77541_BITS_MX_CFG1_RNG, reg_val);
> +
> +		*val = 0;
> +
> +		if (reg_val == LOW_RANGE)

Ah. Here is the mysterious macro from patch 1.  Bring that definition forwards
to this patch.  Also switch statement would be more readable here.

> +			*val2 = 6250;
> +		else if (reg_val == MID_RANGE)
> +			*val2 = 12500;
> +		else if (reg_val == HIGH_RANGE)
> +			*val2 = 25000;
> +		else
> +			return -EINVAL;
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case MAX77541_ADC_VOUT2_V:
> +		ret = regmap_read(info->regmap, MAX77541_REG_M2_CFG1, &reg_val);

Umm. Is this identical to the above case?  If so, just have one block for
both.
  
> +		if (ret)
> +			return ret;
> +		reg_val = FIELD_GET(MAX77541_BITS_MX_CFG1_RNG, reg_val);
> +
> +		*val = 0;
> +
> +		if (reg_val == LOW_RANGE)
> +			*val2 = 6250;
> +		else if (reg_val == MID_RANGE)
> +			*val2 = 12500;
> +		else if (reg_val == HIGH_RANGE)
> +			*val2 = 25000;
> +		else
> +			return -EINVAL;
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case MAX77541_ADC_TEMP:
> +		*val = 1;
> +		*val2 = 725000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +

> +
> +static const struct iio_chan_spec max77541_adc_channels[] = {

Bring the macro definition down to just above this array. That will
make it easier to review as we can see the right parameters are being
passed in.   For 4 channels, I'm not sure I'd bother wrapping it in
a macro at all (particularly as that macro needs to be more
complex - see above), but I don't mind if you want to keep it that way.


I would also move this down below the iio_info definition because
that will keep all the code relevant to that in one place rather
than throwing this in the middle.

> +	MAX77541_ADC_CHANNEL(MAX77541_ADC_VSYS_V, "vsys_v", IIO_VOLTAGE,
> +			     MAX77541_REG_ADC_DATA_CH1),
> +	MAX77541_ADC_CHANNEL(MAX77541_ADC_VOUT1_V, "vout1_v", IIO_VOLTAGE,
> +			     MAX77541_REG_ADC_DATA_CH2),
> +	MAX77541_ADC_CHANNEL(MAX77541_ADC_VOUT2_V, "vout2_v", IIO_VOLTAGE,
> +			     MAX77541_REG_ADC_DATA_CH3),
> +	MAX77541_ADC_CHANNEL(MAX77541_ADC_TEMP, "temp", IIO_TEMP,
> +			     MAX77541_REG_ADC_DATA_CH6),
> +};
> +
> +static int max77541_adc_read_raw(struct iio_dev *indio_dev,
> +				 struct iio_chan_spec const *chan,
> +				 int *val, int *val2, long mask)
> +{
> +	switch (mask) {
> +	case IIO_CHAN_INFO_OFFSET:
> +		return max77541_adc_offset(indio_dev, chan, val, val2);
> +	case IIO_CHAN_INFO_SCALE:
> +		return max77541_adc_scale(indio_dev, chan, val, val2);
> +	case IIO_CHAN_INFO_RAW:
> +		return max77541_adc_raw(indio_dev, chan, val);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info max77541_adc_info = {
> +	.read_raw = max77541_adc_read_raw,
> +};
> +
> +static int max77541_adc_probe(struct platform_device *pdev)
> +{
> +	struct max77541_dev *max77541;
> +	struct max77541_adc_iio *info;
> +	struct iio_dev *indio_dev;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*info));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	info = iio_priv(indio_dev);
> +
> +	info->regmap = max77541->regmap;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	indio_dev->name = platform_get_device_id(pdev)->name;
> +	indio_dev->info = &max77541_adc_info;
> +	indio_dev->channels = max77541_adc_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max77541_adc_channels);
> +
> +	return devm_iio_device_register(&pdev->dev, indio_dev);
> +}
> +
> +static const struct platform_device_id max77541_adc_platform_id[] = {
> +	{ "max77541-adc", MAX77541, },

Better to introduce the complexity given by the type only when it is needed.
So for now drop the .data values here and below.

If / when that does happen I'll be asking you to use a chip_info structure
anyway - right now that structure would be empty so no point in adding it
yet.

> +	{  /* sentinel */  }
> +};
> +MODULE_DEVICE_TABLE(platform, max77541_adc_platform_id);
> +
> +static const struct of_device_id max77541_adc_of_id[] = {
> +	{
> +		.compatible = "adi,max77541-adc",
> +		.data = (void *)MAX77541,
> +	},
> +	{  /* sentinel */  }
> +};
> +MODULE_DEVICE_TABLE(of, max77541_adc_of_id);
> +
> +static struct platform_driver max77541_adc_driver = {
> +	.driver = {
> +		.name = "max77541-adc",
> +		.of_match_table = max77541_adc_of_id,
> +	},
> +	.probe = max77541_adc_probe,
> +	.id_table = max77541_adc_platform_id,
> +};
> +
Drop blank line.  Macro and structure are very closely associated
so it's good to make that obvious by not separating them.
> +module_platform_driver(max77541_adc_driver);
> +
> +MODULE_AUTHOR("Okan Sahin <Okan.Sahin@analog.com>");
> +MODULE_DESCRIPTION("MAX77541 ADC driver");
> +MODULE_LICENSE("GPL");