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Date:   Sun, 2 Apr 2023 18:01:23 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Naresh Solanki <naresh.solanki@9elements.com>
Cc:     Lars-Peter Clausen <lars@metafoo.de>,
        Patrick Rudolph <patrick.rudolph@9elements.com>,
        linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org
Subject: Re: [PATCH v3 1/2] iio: max597x: Add support for max597x
Message-ID: <20230402180123.0fc1cfde@jic23-huawei>
In-Reply-To: <20230328094416.3851801-1-Naresh.Solanki@9elements.com>
References: <20230328094416.3851801-1-Naresh.Solanki@9elements.com>
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On Tue, 28 Mar 2023 11:44:14 +0200
Naresh Solanki <naresh.solanki@9elements.com> wrote:

> From: Patrick Rudolph <patrick.rudolph@9elements.com>
> 
> max5970 & max5978 has 10bit ADC for voltage & current
> monitoring.
> Use iio framework to expose the same in sysfs.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
> Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
> ...

--- not ...

As I mentioned in my reply to v2 thread (which crossed with this v3)
I'd like this series to be cc'd to the list and maintainers for Hwmon
with a cover letter explaining the reasoning for it being an IIO driver
+ the restrictions that potentially brings.

A few other comments inline from taking another look.

Thanks,

Jonathan


> Changes in V3:
> - Use bulk read
> - Remove line split
> Changes in V2:
> - Remove fallthrough
> - Use pdev->dev instead of i2c->dev
> - Init indio_dev->name based on device type.
> ---
>  drivers/iio/adc/Kconfig       |  15 ++++
>  drivers/iio/adc/Makefile      |   1 +
>  drivers/iio/adc/max597x-iio.c | 148 ++++++++++++++++++++++++++++++++++
>  3 files changed, 164 insertions(+)
>  create mode 100644 drivers/iio/adc/max597x-iio.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 45af2302be53..69310af5c665 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -735,6 +735,21 @@ config MAX1363
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1363.
>  
> +config MAX597X_IIO
> +	tristate "Maxim 597x power switch and monitor"
> +	depends on I2C && OF
> +	select MFD_MAX597X
> +	help
> +	  This driver enables support for the Maxim 5970 & 5978 smart switch
> +	  and voltage/current monitoring interface using the Industrial I/O
> +	  (IIO) framework. The Maxim 597x is a power switch and monitor that can
> +	  provide voltage and current measurements via the I2C bus. Enabling
> +	  this driver will allow user space applications to read the voltage
> +	  and current measurements using IIO interfaces.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max597x-iio.
> +
>  config MAX9611
>  	tristate "Maxim max9611/max9612 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 36c18177322a..7ec0c2cf7bbb 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -67,6 +67,7 @@ obj-$(CONFIG_MAX11205) += max11205.o
>  obj-$(CONFIG_MAX11410) += max11410.o
>  obj-$(CONFIG_MAX1241) += max1241.o
>  obj-$(CONFIG_MAX1363) += max1363.o
> +obj-$(CONFIG_MAX597X_IIO) += max597x-iio.o
>  obj-$(CONFIG_MAX9611) += max9611.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
> diff --git a/drivers/iio/adc/max597x-iio.c b/drivers/iio/adc/max597x-iio.c
> new file mode 100644
> index 000000000000..f158e49b5a56
> --- /dev/null
> +++ b/drivers/iio/adc/max597x-iio.c
> @@ -0,0 +1,148 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Device driver for IIO in MAX5970 and MAX5978 IC
> + *
> + * Copyright (c) 2022 9elements GmbH
> + *
> + * Author: Patrick Rudolph <patrick.rudolph@9elements.com>
> + */
> +
> +#include <linux/iio/iio.h>
> +#include <linux/mfd/max597x.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +struct max597x_iio {
> +	struct regmap *regmap;
> +	int shunt_micro_ohms[MAX5970_NUM_SWITCHES];
> +	unsigned int irng[MAX5970_NUM_SWITCHES];
> +	unsigned int mon_rng[MAX5970_NUM_SWITCHES];
> +};
> +
> +#define MAX597X_ADC_CHANNEL(_idx, _type) {			\
> +	.type = IIO_ ## _type,					\
> +	.indexed = 1,						\
> +	.channel = (_idx),					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
> +			      BIT(IIO_CHAN_INFO_SCALE),		\
> +	.address = MAX5970_REG_ ## _type ## _L(_idx),		\
> +}
> +
> +static const struct iio_chan_spec max5978_adc_iio_channels[] = {
> +	MAX597X_ADC_CHANNEL(0, VOLTAGE),
> +	MAX597X_ADC_CHANNEL(0, CURRENT),
> +};
> +
> +static const struct iio_chan_spec max5970_adc_iio_channels[] = {
> +	MAX597X_ADC_CHANNEL(0, VOLTAGE),
> +	MAX597X_ADC_CHANNEL(0, CURRENT),
> +	MAX597X_ADC_CHANNEL(1, VOLTAGE),
> +	MAX597X_ADC_CHANNEL(1, CURRENT),
> +};
> +
> +static int max597x_iio_read_raw(struct iio_dev *iio_dev,
> +				struct iio_chan_spec const *chan,
> +				int *val, int *val2, long info)
> +{
> +	int ret;
> +	struct max597x_iio *data = iio_priv(iio_dev);
> +	u16 reg_l, reg_h;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = regmap_bulk_read(data->regmap, chan->address - 1, &reg_l, 2);

This crossed with my reply to the v2 thread.  If reading two separate registers that
don't directly correspond to a large packed value, read them into an array
of u8.  Then get the relevant parts from that.

The following use is not endian safe (it won't work on a big endian machine)

> +		if (ret < 0)
> +			return ret;
> +		reg_h = reg_l & 0xff;
> +		reg_l = (reg_l >> 8) & 0xff;
> +		*val = (reg_h << 2) | (reg_l & 3);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->address) {
> +		case MAX5970_REG_CURRENT_L(0):
> +		case MAX5970_REG_CURRENT_L(1):
> +			/* in A, convert to mA */
> +			*val = data->irng[chan->channel] * 1000;
> +			*val2 = data->shunt_micro_ohms[chan->channel] * ADC_MASK;
> +			return IIO_VAL_FRACTIONAL;
> +
> +		case MAX5970_REG_VOLTAGE_L(0):
> +		case MAX5970_REG_VOLTAGE_L(1):
> +			/* in uV, convert to mV */
> +			*val = data->mon_rng[chan->channel];
> +			*val2 = ADC_MASK * 1000;
> +			return IIO_VAL_FRACTIONAL;
> +		}
> +
> +		break;
> +	}
> +	return -EINVAL;

I'd prefer this pushed up as a default: in each of the two switch statements.
Makes it clear to compilers and readers that only listing some case values is
deliberate.

> +}
> +
> +static const struct iio_info max597x_adc_iio_info = {
> +	.read_raw = &max597x_iio_read_raw,
> +};
> +
> +static int max597x_iio_probe(struct platform_device *pdev)
> +{
> +	struct max597x_data *max597x = dev_get_drvdata(pdev->dev.parent);
> +	struct regmap *regmap = dev_get_regmap(pdev->dev.parent, NULL);
> +	struct iio_dev *indio_dev;
> +	struct max597x_iio *priv;
> +	int ret, i;
> +
> +	if (!regmap)
> +		return -EPROBE_DEFER;
> +
> +	if (!max597x || !max597x->num_switches)
> +		return -EPROBE_DEFER;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
> +	if (!indio_dev)
> +		return dev_err_probe(&pdev->dev, -ENOMEM,
> +				     "failed to allocate iio device\n");
> +
> +	indio_dev->info = &max597x_adc_iio_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	switch (max597x->num_switches) {

Having a value 'num_switches' that maps to a set of enums called _TYPE_ is unusual.
Perhaps rename it to type.


> +	case MAX597x_TYPE_MAX5970:
> +		indio_dev->channels = max5970_adc_iio_channels;
> +		indio_dev->num_channels = ARRAY_SIZE(max5970_adc_iio_channels);
> +		indio_dev->name = "max5970";
> +		break;
> +	case MAX597x_TYPE_MAX5978:
> +		indio_dev->channels = max5978_adc_iio_channels;
> +		indio_dev->num_channels = ARRAY_SIZE(max5978_adc_iio_channels);
> +		indio_dev->name = "max5978";
> +		break;
> +	}
> +
> +	priv = iio_priv(indio_dev);
> +	priv->regmap = regmap;
> +	for (i = 0; i < indio_dev->num_channels; i++) {
> +		priv->irng[i] = max597x->irng[i];
> +		priv->mon_rng[i] = max597x->mon_rng[i];
> +		priv->shunt_micro_ohms[i] = max597x->shunt_micro_ohms[i];
> +	}
> +
> +	ret = devm_iio_device_register(&pdev->dev, indio_dev);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret, "could not register iio device\n");
> +
> +	return 0;
> +}
> +
> +static struct platform_driver max597x_iio_driver = {
> +	.driver = {
> +		.name = "max597x-iio",
> +	},
> +	.probe = max597x_iio_probe,
> +};
> +
> +module_platform_driver(max597x_iio_driver);
> +
> +MODULE_AUTHOR("Patrick Rudolph <patrick.rudolph@9elements.com>");
> +MODULE_DESCRIPTION("MAX5970_hot-swap controller driver");
> +MODULE_LICENSE("GPL");
> 
> base-commit: 368eb79f738a21e16c2bdbcac2444dfa96b01aaa