[RFC 6/9] iio: ina2xx: add direct IO support for TI INA2xx Power Monitors

[Marc Titinger <mtitinger@baylibre.com>]

Basic support or direct IO raw read, with averaging attribute.
Values are RAW, INT_PLUS_MICRO (Volt/Ampere/Watt).

Output of iio_info:

     iio:device0: ina226
      4 channels found:
        power3:  (input)
        1 channel-specific attributes found:
                attr 0: raw value: 1.150000
        voltage0:  (input)
        1 channel-specific attributes found:
                attr 0: raw value: 0.000003
        voltage1:  (input)
        1 channel-specific attributes found:
                attr 0: raw value: 4.277500
        current2:  (input)
        1 channel-specific attributes found:
                attr 0: raw value: 0.268000
        4 device-specific attributes found:
                attr 0: sampling_frequency_available value: 61 120 236...
                attr 1: in_averaging_steps value: 4
                attr 2: in_calibscale value: 10000
                attr 3: in_sampling_frequency value: 1506

Tested with ina226, on BeagleBoneBlack.

Datasheet: http://www.ti.com/lit/gpn/ina226

Signed-off-by: Marc Titinger <mtitinger@baylibre.com>
---
 drivers/iio/adc/Kconfig      |   9 +
 drivers/iio/adc/Makefile     |   1 +
 drivers/iio/adc/ina2xx-iio.c | 515 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 525 insertions(+)
 create mode 100644 drivers/iio/adc/ina2xx-iio.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 50c103d..ebbfff9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -183,6 +183,15 @@ config EXYNOS_ADC
 	  To compile this driver as a module, choose M here: the module will be
 	  called exynos_adc.
 
+config INA2XX_IIO
+	tristate "Texas Instruments INA2xx Power Monitors IIO driver"
+	depends on I2C
+	select REGMAP_I2C
+	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..d4dd908
--- /dev/null
+++ b/drivers/iio/adc/ina2xx-iio.c
@@ -0,0 +1,515 @@
+/*
+ * 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@ti.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/iio/iio.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
+
+/* 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_FREQ             455
+
+#define INA2XX_RSHUNT_DEFAULT           10000
+
+/* bit mask for reading the averaging setting in the configuration register */
+#define INA226_AVG_RD_MASK              GENMASK(11, 9)
+#define INA226_READ_AVG(reg)            (((reg) & INA226_AVG_RD_MASK) >> 9)
+#define INA226_SHIFT_AVG(val)           ((val) << 9)
+
+#define INA226_SFREQ_RD_MASK            GENMASK(8, 3)
+
+
+static bool ina2xx_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	return (reg == INA2XX_CONFIG) || (reg == INA2XX_CALIBRATION);
+}
+
+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 {
+	const struct ina2xx_config *config;
+	struct mutex state_lock;
+	long rshunt;
+	int avg;
+	int freq;
+	int period_us;
+	struct regmap *regmap;
+};
+
+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;
+
+	case INA2XX_CALIBRATION:
+		*val = DIV_ROUND_CLOSEST(chip->config->calibration_factor,
+					regval);
+		return IIO_VAL_INT;
+
+	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_AVERAGE_RAW:
+		*val = chip->avg;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_CALIBSCALE:
+		ret = regmap_read(chip->regmap, INA2XX_CALIBRATION, &regval);
+		if (ret < 0)
+			return ret;
+
+		return ina2xx_get_value(chip, INA2XX_CALIBRATION, regval,
+					val, val2);
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = chip->freq;
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int ina2xx_calibrate(struct ina2xx_chip_info *chip)
+{
+	u16 val = DIV_ROUND_CLOSEST(chip->config->calibration_factor,
+				    chip->rshunt);
+
+	return regmap_write(chip->regmap, INA2XX_CALIBRATION, val);
+}
+
+
+/*
+ * 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_RD_MASK;
+	*config |= INA226_SHIFT_AVG(bits) & INA226_AVG_RD_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_frequency(struct ina2xx_chip_info *chip,
+					 unsigned int val,
+					 unsigned int *config)
+{
+	int bits;
+
+	if (val > 3550  || val < 50)
+		return -EINVAL;
+
+	/* integration time in uS, for both voltage channels */
+	val = DIV_ROUND_CLOSEST(1000000, 2 * val);
+
+	bits = find_closest(val, ina226_conv_time_tab,
+			    ARRAY_SIZE(ina226_conv_time_tab));
+
+	chip->period_us = 2 * ina226_conv_time_tab[bits];
+
+	chip->freq = DIV_ROUND_CLOSEST(1000000, chip->period_us);
+
+	*config &= ~INA226_SFREQ_RD_MASK;
+	*config |= (bits << 3) | (bits << 6);
+
+	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;
+
+	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_AVERAGE_RAW:
+
+		ret = ina226_set_average(chip, val, &tmp);
+		break;
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+
+		ret = ina226_set_frequency(chip, val, &tmp);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	if (!ret && (tmp != config))
+		ret = regmap_write(chip->regmap, INA2XX_CONFIG, config);
+_err:
+	mutex_unlock(&chip->state_lock);
+
+	return ret;
+}
+
+
+static ssize_t ina2xx_averaging_steps_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct ina2xx_chip_info *chip = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%d\n", chip->avg);
+}
+
+
+static ssize_t ina2xx_averaging_steps_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t len)
+{
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul((const char *) buf, 10, &val);
+	if (ret)
+		return -EINVAL;
+
+	/* unexposed missuse of INFO_AVERAGE_RAW, until a proper ABI for the
+	 * averaging steps setting is specified.
+	 */
+	ret  = ina2xx_write_raw(dev_to_iio_dev(dev), NULL, val, 0,
+				IIO_CHAN_INFO_AVERAGE_RAW);
+	if (ret < 0)
+		return ret;
+
+	return len;
+}
+
+
+#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_CALIBSCALE), \
+	.scan_index = (_index), \
+	.scan_type = { \
+		.sign = 'u', \
+		.realbits = 16, \
+		.storagebits = 16, \
+		.shift = 0, \
+	.endianness = IIO_BE, \
+	} \
+}
+
+static const struct iio_chan_spec ina2xx_channels[] = {
+	INA2XX_CHAN(IIO_VOLTAGE, 0, INA2XX_SHUNT_VOLTAGE),
+	INA2XX_CHAN(IIO_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 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 */
+static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("61 120 236 455 850 1506 2450 3571");
+
+static IIO_DEVICE_ATTR(in_averaging_steps, S_IRUGO | S_IWUSR,
+		       ina2xx_averaging_steps_show,
+		       ina2xx_averaging_steps_store, 0);
+
+static struct attribute *ina2xx_attributes[] = {
+	&iio_dev_attr_in_averaging_steps.dev_attr.attr,
+	&iio_const_attr_sampling_frequency_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)
+{
+	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).
+	 */
+	return ina2xx_calibrate(chip);
+}
+
+static int ina2xx_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct ina2xx_chip_info *chip;
+	struct iio_dev *indio_dev;
+	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);
+
+	/* set the device type */
+	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;
+
+	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_frequency(chip, INA226_DEFAULT_FREQ, &val);
+	}
+
+	ret = ina2xx_init(chip, val);
+	if (ret < 0) {
+		dev_err(&client->dev, "error configuring the device: %d\n",
+			ret);
+		return -ENODEV;
+	}
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+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,
+	.id_table = ina2xx_id,
+};
+
+module_i2c_driver(ina2xx_driver);
+
+MODULE_AUTHOR("Marc Titinger <marc.titinger@baylibre.com>");
+MODULE_DESCRIPTION("Texas Instruments INA2XX ADC driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1