Message-ID: <565B287B.6010008@kernel.org>
Date:	Sun, 29 Nov 2015 16:31:55 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Marc Titinger <mtitinger@...libre.com>, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net, linux@...ck-us.net,
	jdelvare@...e.com
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	lm-sensors@...sensors.org
Subject: Re: [PATCH 1/2] iio: ina2xx: add support for TI INA2xx Power Monitors

On 25/11/15 11:28, Marc Titinger wrote:
> in SOFTWARE buffer mode, a kthread will capture the active scan_elements
> into a kfifo, then compute the remaining time until the next capture tick
> and do an active wait (udelay).
> 
> This will produce a stream of up to fours channels plus a 64bits
> timestamps (ns).
> 
> Tested with ina226, on BeagleBoneBlack.
> 
> Datasheet: http://www.ti.com/lit/gpn/ina226
> 
> Signed-off-by: Marc Titinger <mtitinger@...libre.com>
A few more bits from me, but basically looking good.

We do however, need to make the hwmon guys aware this is going on.
Please cc their list on the next version.

Last thing we want is for this to turn up as a surprise!

Jonathan
> ---
>  drivers/iio/adc/Kconfig      |  10 +
>  drivers/iio/adc/Makefile     |   1 +
>  drivers/iio/adc/ina2xx-iio.c | 684 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 695 insertions(+)
>  create mode 100644 drivers/iio/adc/ina2xx-iio.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index eb0cd89..9b87372 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -170,6 +170,16 @@ config EXYNOS_ADC
>  	  of SoCs for drivers such as the touchscreen and hwmon to use to share
>  	  this resource.
>  
> +config INA2XX_IIO
> +	tristate "Texas Instruments INA2xx Power Monitors IIO driver"
> +	depends on I2C
> +	select REGMAP_I2C
> +	select IIO_BUFFER
> +	help
> +	  Say yes here to build support for TI INA2xx familly Power Monitors.
> +
> +	  Note that this is not the existing hwmon interface for this device.
> +
>  config LP8788_ADC
>  	tristate "LP8788 ADC driver"
>  	depends on MFD_LP8788
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index a096210..74e4341 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
>  obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
>  obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
>  obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
> +obj-$(CONFIG_INA2XX_IIO) += ina2xx-iio.o
>  obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX1363) += max1363.o
> diff --git a/drivers/iio/adc/ina2xx-iio.c b/drivers/iio/adc/ina2xx-iio.c
> new file mode 100644
> index 0000000..4a0026c
> --- /dev/null
> +++ b/drivers/iio/adc/ina2xx-iio.c
> @@ -0,0 +1,684 @@
> +/*
> + * INA2XX Current and Power Monitors
> + *
> + * Copyright 2015 Baylibre SAS.
> + *
> + * 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.
> + *
> + * Based on linux/drivers/iio/adc/ad7291.c
> + * Copyright 2010-2011 Analog Devices Inc.
> + *
> + * Based on linux/drivers/hwmon/ina2xx.c
> + * Copyright 2012 Lothar Felten <l-felten@...com>
> + *
> + * Licensed under the GPL-2 or later.
> + *
> + * IIO driver for INA219-220-226-230-231
> + *
> + * Configurable 7-bit I2C slave address from 0x40 to 0x4F
> + */
> +#include <linux/module.h>
> +#include <linux/kthread.h>
> +#include <linux/delay.h>
> +#include <linux/iio/kfifo_buf.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/i2c.h>
> +#include <linux/regmap.h>
> +#include <linux/platform_data/ina2xx.h>
> +
> +#include <linux/util_macros.h>
> +
> +/*
> + * INA2XX registers definition
> + */
> +/* common register definitions */
> +#define INA2XX_CONFIG                   0x00
> +#define INA2XX_SHUNT_VOLTAGE            0x01	/* readonly */
> +#define INA2XX_BUS_VOLTAGE              0x02	/* readonly */
> +#define INA2XX_POWER                    0x03	/* readonly */
> +#define INA2XX_CURRENT                  0x04	/* readonly */
> +#define INA2XX_CALIBRATION              0x05
> +
> +#define INA226_ALERT_MASK		0x06
> +#define INA266_CVRF			BIT(3)
> +
> +/* register count */
> +#define INA219_REGISTERS                6
> +#define INA226_REGISTERS                8
> +#define INA2XX_MAX_REGISTERS            8
> +
> +/* settings - depend on use case */
> +#define INA219_CONFIG_DEFAULT           0x399F	/* PGA=8 */
> +#define INA226_CONFIG_DEFAULT           0x4327
> +#define INA226_DEFAULT_AVG              4
> +#define INA226_DEFAULT_IT		1110
> +
> +#define INA2XX_RSHUNT_DEFAULT           10000
> +
> +/*
> + * bit mask for reading the averaging setting in the configuration register
> + * FIXME: use regmap_fields.
> + */
> +#define INA2XX_MODE_MASK	GENMASK(3, 0)
> +
> +#define INA226_AVG_MASK		GENMASK(11, 9)
> +#define INA226_SHIFT_AVG(val)	((val) << 9)
> +
> +/* Integration time for VBus */
> +#define INA226_ITB_MASK		GENMASK(8, 6)
> +#define INA226_SHIFT_ITB(val)	((val) << 6)
> +
> +/*Integration Time for VShunt */
> +#define INA226_ITS_MASK		GENMASK(5, 3)
> +#define INA226_SHIFT_ITS(val)	((val) << 3)
> +
> +
> +static bool ina2xx_is_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	return (reg == INA2XX_CONFIG) || (reg > INA2XX_CURRENT);
> +}
> +
> +static bool ina2xx_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	return (reg != INA2XX_CONFIG);
> +}
> +
> +static struct regmap_config ina2xx_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +
> +	.writeable_reg = ina2xx_is_writeable_reg,
> +	.volatile_reg = ina2xx_is_volatile_reg,
> +};
> +
> +enum ina2xx_ids { ina219, ina226 };
> +
> +struct ina2xx_config {
> +	u16 config_default;
> +	int calibration_factor;
> +	int registers;
> +	int shunt_div;
> +	int bus_voltage_shift;
> +	int bus_voltage_lsb;	/* uV */
> +	int power_lsb;		/* uW */
> +};
> +
> +struct ina2xx_chip_info {
> +	struct regmap *regmap;
> +	struct task_struct *task;
> +	const struct ina2xx_config *config;
> +	struct mutex state_lock;
> +	long rshunt;
> +	int avg;
> +	int itb; /* Bus voltage integration time uS */
> +	int its; /* Shunt voltage integration tim uS */
> +};
> +
> +static const struct ina2xx_config ina2xx_config[] = {
> +	[ina219] = {
> +		    .config_default = INA219_CONFIG_DEFAULT,
> +		    .calibration_factor = 40960000,
> +		    .registers = INA219_REGISTERS,
> +		    .shunt_div = 100,
> +		    .bus_voltage_shift = 3,
> +		    .bus_voltage_lsb = 4000,
> +		    .power_lsb = 20000,
> +		    },
> +	[ina226] = {
> +		    .config_default = INA226_CONFIG_DEFAULT,
> +		    .calibration_factor = 5120000,
> +		    .registers = INA226_REGISTERS,
> +		    .shunt_div = 400,
> +		    .bus_voltage_shift = 0,
> +		    .bus_voltage_lsb = 1250,
> +		    .power_lsb = 25000,
> +		    },
> +};
> +
> +static int ina2xx_get_value(struct ina2xx_chip_info *chip, u8 reg,
> +			    unsigned int regval, int *val, int *uval)
> +{
> +	*val = 0;
> +
> +	switch (reg) {
> +	case INA2XX_SHUNT_VOLTAGE:
> +		/* signed register */
> +		*uval = DIV_ROUND_CLOSEST((s16) regval,
> +					  chip->config->shunt_div);
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	case INA2XX_BUS_VOLTAGE:
> +		*uval = (regval >> chip->config->bus_voltage_shift)
> +			* chip->config->bus_voltage_lsb;
> +		*val = *uval/1000000;
> +		*uval = *uval % 1000000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	case INA2XX_POWER:
> +		*uval = regval * chip->config->power_lsb;
> +		*val = *uval/1000000;
> +		*uval = *uval % 1000000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	case INA2XX_CURRENT:
> +		/* signed register, LSB=1mA (selected), in mA */
> +		*uval = (s16) regval * 1000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	default:
> +		/* programmer goofed */
> +		WARN_ON_ONCE(1);
> +	}
> +	return -EINVAL;
> +}
> +
> +static int ina2xx_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	int ret;
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	unsigned int regval;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = regmap_read(chip->regmap, chan->address, &regval);
> +		if (ret < 0)
> +			return ret;
> +
> +		return ina2xx_get_value(chip, chan->address, regval, val, val2);
> +
> +	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> +		*val = chip->avg;
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_INT_TIME:
> +		*val = 0;
> +		if (chan->address == INA2XX_SHUNT_VOLTAGE)
> +			*val2 = chip->its;
> +		else
> +			*val2 = chip->itb;
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	/*
> +	 * sample freq is read only, it is a consequence of
> +	 * 1/AVG*(CT_bus+CT_shunt)
> +	 */
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val = DIV_ROUND_CLOSEST(1000000,
> +		       (chip->itb + chip->its) * chip->avg);
> +
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Available averaging rates for ina226. The indices correspond with
> + * the bit values expected by the chip (according to the ina226 datasheet,
> + * table 3 AVG bit settings, found at
> + * http://www.ti.com/lit/ds/symlink/ina226.pdf.
> + */
> +static const int ina226_avg_tab[] = { 1, 4, 16, 64, 128, 256, 512, 1024 };
> +
> +static unsigned int ina226_set_average(struct ina2xx_chip_info *chip,
> +				       unsigned int val,
> +				       unsigned int *config)
> +{
> +	int bits;
> +
> +	if (val > 1024 || val < 1)
> +		return -EINVAL;
> +
> +	bits = find_closest(val, ina226_avg_tab,
> +			    ARRAY_SIZE(ina226_avg_tab));
> +
> +	chip->avg = ina226_avg_tab[bits];
> +
> +	*config &= ~INA226_AVG_MASK;
> +	*config |= INA226_SHIFT_AVG(bits) & INA226_AVG_MASK;
> +
> +	return 0;
> +}
> +
> +/* Conversion times in uS */
> +static const int ina226_conv_time_tab[] = { 140, 204, 332, 588, 1100,
> +					    2116, 4156, 8244};
> +
> +static unsigned int ina226_set_itb(struct ina2xx_chip_info *chip,
> +				   unsigned int val,
> +				   unsigned int *config)
> +{
> +	int bits;
> +
> +	if (val > 8244 || val < 140)
> +		return -EINVAL;
> +
> +	bits = find_closest(val, ina226_conv_time_tab,
> +			ARRAY_SIZE(ina226_conv_time_tab));
> +
> +	chip->itb = ina226_conv_time_tab[bits];
> +
> +	*config &= ~INA226_ITB_MASK;
> +	*config |= INA226_SHIFT_ITB(bits) & INA226_ITB_MASK;
> +
> +	return 0;
> +}
> +
Could do with a slightly more informative name than its vs itb.
Or at least some docs explaining what it does.
> +static unsigned int ina226_set_its(struct ina2xx_chip_info *chip,
> +				   unsigned int val,
> +				   unsigned int *config)
> +{
> +	int bits;
> +
> +	if (val > 8244 || val < 140)
> +		return -EINVAL;
> +
> +	bits = find_closest(val, ina226_conv_time_tab,
> +			ARRAY_SIZE(ina226_conv_time_tab));
> +
> +	chip->its = ina226_conv_time_tab[bits];
> +
> +	*config &= ~INA226_ITS_MASK;
> +	*config |= INA226_SHIFT_ITS(bits) & INA226_ITS_MASK;
> +
> +	return 0;
> +}
> +
> +
> +static int ina2xx_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	int ret = 0;
> +	unsigned int config, tmp;
> +
> +	if (iio_buffer_enabled(indio_dev))
> +		return -EBUSY;
> +
> +	mutex_lock(&chip->state_lock);
> +
> +	ret = regmap_read(chip->regmap, INA2XX_CONFIG, &config);
> +	if (ret < 0)
> +		goto _err;
> +
> +	tmp = config;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> +		ret = ina226_set_average(chip, val, &tmp);
> +		break;
> +
> +	case IIO_CHAN_INFO_INT_TIME:
> +		if (chan->address == INA2XX_SHUNT_VOLTAGE)
> +			ret = ina226_set_its(chip, val, &tmp);
> +		else
> +			ret = ina226_set_itb(chip, val, &tmp);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
> +	if (!ret && (tmp != config))
> +		ret = regmap_write(chip->regmap, INA2XX_CONFIG, tmp);
> +_err:
> +	mutex_unlock(&chip->state_lock);
> +
> +	return ret;
> +}
> +
> +
> +#define INA2XX_CHAN(_type, _index, _address) { \
> +	.type = _type, \
> +	.address = _address, \
> +	.indexed = 1, \
> +	.channel = (_index), \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +	.info_mask_shared_by_dir = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
> +				   BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> +	.scan_index = (_index), \
> +	.scan_type = { \
> +		.sign = 'u', \
> +		.realbits = 16, \
> +		.storagebits = 16, \
> +	.endianness = IIO_BE, \
> +	} \
> +}
> +
> +/*Sampling Freq is a consequence of the integration times of the V channels.*/
> +#define INA2XX_CHAN_VOLTAGE(_index, _address) { \
> +	.type = IIO_VOLTAGE, \
> +	.address = _address, \
> +	.indexed = 1, \
> +	.channel = (_index), \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> +			      BIT(IIO_CHAN_INFO_INT_TIME), \
> +	.scan_index = (_index), \
> +	.scan_type = { \
> +		.sign = 'u', \
> +		.realbits = 16, \
> +		.storagebits = 16, \
> +	.endianness = IIO_BE, \
> +	} \
> +}
> +
> +
> +static const struct iio_chan_spec ina2xx_channels[] = {
> +	INA2XX_CHAN_VOLTAGE(0, INA2XX_SHUNT_VOLTAGE),
> +	INA2XX_CHAN_VOLTAGE(1, INA2XX_BUS_VOLTAGE),
> +	INA2XX_CHAN(IIO_CURRENT, 2, INA2XX_CURRENT),
> +	INA2XX_CHAN(IIO_POWER, 3, INA2XX_POWER),
> +	IIO_CHAN_SOFT_TIMESTAMP(4),
> +};
> +
> +
> +static s64 prev_ns;
This prevents you having more than one instance of the device - move it into
your chip_info.
> +
> +static int ina2xx_work_buffer(struct iio_dev *indio_dev)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	unsigned short data[8];
> +	int bit, ret = 0, i = 0;
> +	unsigned long buffer_us = 0, elapsed_us = 0;
> +	s64 time_a, time_b;
> +	unsigned int alert;
> +
> +	time_a = iio_get_time_ns();
> +
> +	/*
> +	 * Because the timer thread and the chip conversion clock
> +	 * are asynchronous, the period difference will eventually
> +	 * result in reading V[k-1] again, or skip V[k] at time Tk.
> +	 * In order to resync the timer with the conversion process
> +	 * we check the ConVersionReadyFlag.
> +	 * On hardware that supports using the ALERT pin to toggle a
> +	 * GPIO a triggered buffer could be used instead.
> +	 * For now, we pay for that extra read of the ALERT register
> +	 */
> +	do {
> +		ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
> +				  &alert);
> +		if (ret < 0)
> +			goto _err;
> +
> +		alert &= INA266_CVRF;
> +		trace_printk("Conversion ready: %d\n", !!alert);
> +
> +	} while (!alert);
> +
> +	/*
> +	 * Single register reads: bulk_read will not work with ina226
> +	 * as there is no auto-increment of the address register for
> +	 * data length longer than 16bits.
> +	 */
> +	for_each_set_bit(bit, indio_dev->active_scan_mask,
> +			 indio_dev->masklength) {
> +		unsigned int val;
> +
> +		ret = regmap_read(chip->regmap,
> +				  INA2XX_SHUNT_VOLTAGE + bit, &val);
> +		if (ret < 0)
> +			goto _err;
> +
> +		data[i++] = val;
> +	}
> +
> +	time_b = iio_get_time_ns();
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev,
> +					   (unsigned int *)data, time_a);
> +
> +	buffer_us = (unsigned long)(time_b - time_a) / 1000;
> +	elapsed_us = (unsigned long)(time_a - prev_ns) / 1000;
> +
> +	trace_printk("uS: elapsed: %lu, buf: %lu\n", elapsed_us, buffer_us);
> +
> +	prev_ns = time_a;
> +
> +_err:
> +	return buffer_us;
> +};
> +
> +static int ina2xx_capture_thread(void *data)
> +{
> +	struct iio_dev *indio_dev = (struct iio_dev *)data;
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	unsigned int sampling_us = (chip->itb + chip->its) * chip->avg;
> +	unsigned long buffer_us;
> +
> +	/*
> +	 * Poll a bit faster than the chip internal Fs, in case
> +	 * we wish to sync with the conversion ready flag.
> +	 */
> +	sampling_us -= 200;
> +
> +	do {
> +		buffer_us = ina2xx_work_buffer(indio_dev);
> +
> +		if (sampling_us > buffer_us)
> +			udelay(sampling_us - buffer_us);
> +
> +	} while (!kthread_should_stop());
> +
> +	return 0;
> +}
> +
> +int ina2xx_buffer_enable(struct iio_dev *indio_dev)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	unsigned int sampling_us = (chip->itb + chip->its) * chip->avg;
> +
> +	trace_printk("Enabling buffer w/ scan_mask %02x, freq = %d, avg =%u\n",
> +		     (unsigned int)(*indio_dev->active_scan_mask),
> +		     1000000/sampling_us, chip->avg);
> +
> +	trace_printk("Expected work period: %u us\n", sampling_us);
> +
> +	prev_ns = iio_get_time_ns();
> +
> +	chip->task = kthread_run(ina2xx_capture_thread, (void *)indio_dev,
> +				 "ina2xx-%uus", sampling_us);
> +
> +	return PTR_ERR_OR_ZERO(chip->task);
> +}
> +
> +int ina2xx_buffer_disable(struct iio_dev *indio_dev)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +
> +	if (chip->task) {
> +		kthread_stop(chip->task);
> +		chip->task = NULL;
> +	}
nitpick: blank line here.
> +	return 0;
> +}
> +
> +static const struct iio_buffer_setup_ops ina2xx_setup_ops = {
> +	.postenable = &ina2xx_buffer_enable,
> +	.postdisable = &ina2xx_buffer_disable,
> +};
> +
> +static int ina2xx_debug_reg(struct iio_dev *indio_dev,
> +			    unsigned reg, unsigned writeval, unsigned *readval)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +
> +	if (!readval)
> +		return regmap_write(chip->regmap, reg, writeval);
> +
> +	return regmap_read(chip->regmap, reg, readval);
> +}
> +
> +/* frequencies matching the cummulated integration times for vshunt and vbus */
huh?  Integration time is in seconds... These seem unlikely to be valid
settings.
> +static IIO_CONST_ATTR_INT_TIME_AVAIL("140 204 332 588 1100 2116 4156 8244");
> +
> +static struct attribute *ina2xx_attributes[] = {
> +	&iio_const_attr_integration_time_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group ina2xx_attribute_group = {
> +	.attrs = ina2xx_attributes,
> +};
> +
> +static const struct iio_info ina2xx_info = {
> +	.debugfs_reg_access = &ina2xx_debug_reg,
> +	.read_raw = &ina2xx_read_raw,
> +	.write_raw = &ina2xx_write_raw,
> +	.attrs = &ina2xx_attribute_group,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +/* Initialize the configuration and calibration registers. */
> +static int ina2xx_init(struct ina2xx_chip_info *chip, unsigned int config)
> +{
> +	u16 regval;
> +	int ret = regmap_write(chip->regmap, INA2XX_CONFIG, config);
> +
> +	if (ret < 0)
> +		return ret;
> +	/*
> +	 * Set current LSB to 1mA, shunt is in uOhms
> +	 * (equation 13 in datasheet). We hardcode a Current_LSB
> +	 * of 1.0 x10-6. The only remaining parameter is RShunt
> +	 * There is no need to expose the CALIBRATION register
> +	 * to the user for now.
> +	 */
> +	regval = DIV_ROUND_CLOSEST(chip->config->calibration_factor,
> +			    chip->rshunt);
> +
> +	return regmap_write(chip->regmap, INA2XX_CALIBRATION, regval);
> +}
> +
> +static int ina2xx_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct ina2xx_chip_info *chip;
> +	struct iio_dev *indio_dev;
> +	struct iio_buffer *buffer;
> +	int ret;
> +	unsigned int val;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*chip));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	chip = iio_priv(indio_dev);
> +
> +	chip->config = &ina2xx_config[id->driver_data];
> +
> +	if (of_property_read_u32(client->dev.of_node,
> +				 "shunt-resistor", &val) < 0) {
> +		struct ina2xx_platform_data *pdata =
> +		    dev_get_platdata(&client->dev);
> +
> +		if (pdata)
> +			val = pdata->shunt_uohms;
> +		else
> +			val = INA2XX_RSHUNT_DEFAULT;
> +	}
> +
> +	if (val <= 0 || val > chip->config->calibration_factor)
> +		return -ENODEV;
> +
> +	chip->rshunt = val;
> +
> +	ina2xx_regmap_config.max_register = chip->config->registers;
> +
> +	mutex_init(&chip->state_lock);
> +
> +	/* this is only used for device removal purposes */
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	indio_dev->name = id->name;
> +	indio_dev->channels = ina2xx_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(ina2xx_channels);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &ina2xx_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
> +
> +	chip->regmap = devm_regmap_init_i2c(client, &ina2xx_regmap_config);
> +	if (IS_ERR(chip->regmap)) {
> +		dev_err(&client->dev, "failed to allocate register map\n");
> +		return PTR_ERR(chip->regmap);
> +	}
> +
> +	/* Patch the current config register with default. */
> +	val = chip->config->config_default;
> +
> +	if (id->driver_data == ina226) {
> +		ina226_set_average(chip, INA226_DEFAULT_AVG, &val);
> +		ina226_set_itb(chip, INA226_DEFAULT_IT, &val);
> +		ina226_set_its(chip, INA226_DEFAULT_IT, &val);
> +	}
> +
> +	ret = ina2xx_init(chip, val);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "error configuring the device: %d\n",
> +			ret);
> +		return -ENODEV;
> +	}
> +
> +	buffer = devm_iio_kfifo_allocate(&indio_dev->dev);
> +	if (!buffer)
> +		return -ENOMEM;
> +
> +	indio_dev->setup_ops = &ina2xx_setup_ops;
> +
> +	iio_device_attach_buffer(indio_dev, buffer);
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +
> +static int ina2xx_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_destroy(&chip->state_lock);
> +
> +	/* Powerdown */
> +	ret = regmap_update_bits(chip->regmap, INA2XX_CONFIG,
> +				  INA2XX_MODE_MASK, 0);
> +
> +	iio_device_unregister(indio_dev);
Peter already covered this to a degree.

iio_device_unregister removes the userspace interface - hence it
must be the first thing done in remove.

If you use devm_ version of register it will occur at the end of the
remove.  Hence if the remove has anything in it, you pretty much
can't use the devm_iio_device_register without introducing a nasty
race condition.  Hence you don't want the devm version here and you
want to move iio_device_unregister to the beginning of this function.
> +
> +	return ret;
> +}
> +
> +
> +static const struct i2c_device_id ina2xx_id[] = {
> +	{"ina219", ina219},
> +	{"ina220", ina219},
> +	{"ina226", ina226},
> +	{"ina230", ina226},
> +	{"ina231", ina226},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, ina2xx_id);
> +
> +static struct i2c_driver ina2xx_driver = {
> +	.driver = {
> +		   .name = KBUILD_MODNAME,
> +	},
> +	.probe = ina2xx_probe,
> +	.remove = ina2xx_remove,
> +	.id_table = ina2xx_id,
> +};
> +
> +module_i2c_driver(ina2xx_driver);
> +
> +MODULE_AUTHOR("Marc Titinger <marc.titinger@...libre.com>");
> +MODULE_DESCRIPTION("Texas Instruments INA2XX ADC driver");
> +MODULE_LICENSE("GPL v2");
> 

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