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
      2 device-specific attributes found:
                attr 0: in_calibscale value: 10000
                attr 1: in_mean_raw value: 4
                attr 2: in_sampling_frequency value: 455

Tested with ina226, on BeagleBoneBlack.

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

Signed-off-by: Marc Titinger <mtitin...@baylibre.com>
---

v2 of series https://lkml.org/lkml/2015/11/10/370 :

        - squash patches adding SAMPL_FREQ and debugfs interface
        - add regmap is_volatile and is_writeable callbacks
        - fix Kconfig deps and alphabetical sorting
        - simplification: use devm_iio_device_register

---

 drivers/iio/adc/Kconfig      |   9 +
 drivers/iio/adc/Makefile     |   1 +
 drivers/iio/adc/ina2xx-iio.c | 472 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 482 insertions(+)
 create mode 100644 drivers/iio/adc/ina2xx-iio.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index eb0cd89..087e5bd 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -170,6 +170,15 @@ 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
+       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..28b7919
--- /dev/null
+++ b/drivers/iio/adc/ina2xx-iio.c
@@ -0,0 +1,472 @@
+/*
+ * 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-fel...@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/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             454
+
+#define INA2XX_RSHUNT_DEFAULT           10000
+
+/* bit mask for reading the averaging setting in the configuration register */
+#define INA226_AVG_RD_MASK              0x0E00
+#define INA226_READ_AVG(reg)            (((reg) & INA226_AVG_RD_MASK) >> 9)
+#define INA226_SHIFT_AVG(val)           ((val) << 9)
+
+#define INA226_SFREQ_RD_MASK            0x01f8
+
+
+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 {
+       struct iio_dev *indio_dev;
+       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);
+               *val = *uval/1000000;
+               *uval = *uval - *val*1000000;
+               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 - *val*1000000;
+               return IIO_VAL_INT_PLUS_MICRO;
+
+       case INA2XX_POWER:
+               *uval = regval * chip->config->power_lsb;
+               *val = *uval/1000000;
+               *uval = *uval - *val*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;
+}
+
+#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_AVERAGE_RAW) | \
+                                       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);
+}
+
+static const struct iio_info ina2xx_info = {
+       .debugfs_reg_access = &ina2xx_debug_reg,
+       .read_raw = &ina2xx_read_raw,
+       .write_raw = &ina2xx_write_raw,
+       .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);
+       chip->indio_dev = 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.titin...@baylibre.com>");
+MODULE_DESCRIPTION("Texas Instruments INA2XX ADC driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

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