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

  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

Signed-off-by: Okan Sahin <okan.sahin@analog.com>
---
 MAINTAINERS                    |   1 +
 drivers/iio/adc/Kconfig        |  11 ++
 drivers/iio/adc/Makefile       |   1 +
 drivers/iio/adc/max77541-adc.c | 224 +++++++++++++++++++++++++++++++++
 4 files changed, 237 insertions(+)
 create mode 100644 drivers/iio/adc/max77541-adc.c
  

On Wed, Dec 07, 2022 at 12:08:44PM +0300, Okan Sahin 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

Same comment as per patch 2.

...

> +#include <linux/bitfield.h>
> +#include <linux/iio/iio.h>

> +#include <include/linux/mfd/max77541.h>

Hmm...

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

...

> +enum {
> +	MAX77541_ADC_CH1_I = 0,
> +	MAX77541_ADC_CH2_I,
> +	MAX77541_ADC_CH3_I,
> +	MAX77541_ADC_CH6_I,
> +
> +	MAX77541_ADC_IRQMAX_I,

If it's a terminator, drop the trailing comma.

> +};

...

> +	case MAX77541_ADC_TEMP:
> +		*val = -273;

I believe we have definition for this in units.h. Can you use it?

> +		*val2 = 0;
> +		return IIO_VAL_INT_PLUS_MICRO;


> +	}
> +}

...

> +		*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;

Can it be provided as a table?

...

> +		*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;

Ditto.

...

> +

Redundant blank line.

> +module_platform_driver(max77541_adc_driver);
  

Hi Okan,

I love your patch! Yet something to improve:

[auto build test ERROR on staging/staging-testing]

url:    https://github.com/intel-lab-lkp/linux/commits/Okan-Sahin/staging-drivers-mfd-Add-MAX77541-MFD-and-related-device-drivers/20221207-171559
patch link:    https://lore.kernel.org/r/20221207090906.5896-6-okan.sahin%40analog.com
patch subject: [PATCH 5/5] staging: drivers: iio: adc: Adc MAX77541 ADC Support
config: s390-allyesconfig
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/37b9db52db8439588f267900b71bf61c294e8e6f
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Okan-Sahin/staging-drivers-mfd-Add-MAX77541-MFD-and-related-device-drivers/20221207-171559
        git checkout 37b9db52db8439588f267900b71bf61c294e8e6f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> drivers/iio/adc/max77541-adc.c:9:10: fatal error: include/linux/mfd/max77541.h: No such file or directory
       9 | #include <include/linux/mfd/max77541.h>
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   compilation terminated.


vim +9 drivers/iio/adc/max77541-adc.c

   > 9	#include <include/linux/mfd/max77541.h>
    10	#include <linux/platform_device.h>
    11	#include <linux/regmap.h>
    12	#include <linux/regulator/driver.h>
    13	#include <linux/regulator/of_regulator.h>
    14
  

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");