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Date:   Thu, 30 Aug 2018 22:18:22 +0100
From:   Afonso Bordado <afonsobordado@....co>
To:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: [PATCH v2 1/4] iio: gyro: add support for fxas21002c

FXAS21002C is a 3 axis gyroscope with integrated temperature sensor

Signed-off-by: Afonso Bordado <afonsobordado@....co>
---
 Changes in v2
   - Use ANSI C Comments
   - Minor cleanups
   - More dscriptive devicetree bindings

 drivers/iio/gyro/Kconfig      |  11 +
 drivers/iio/gyro/Makefile     |   1 +
 drivers/iio/gyro/fxas21002c.c | 367 ++++++++++++++++++++++++++++++++++
 3 files changed, 379 insertions(+)
 create mode 100644 drivers/iio/gyro/fxas21002c.c

diff --git a/drivers/iio/gyro/Kconfig b/drivers/iio/gyro/Kconfig
index 3126cf05e6b9..d71e33ea9fa4 100644
--- a/drivers/iio/gyro/Kconfig
+++ b/drivers/iio/gyro/Kconfig
@@ -73,6 +73,17 @@ config BMG160_SPI
 	tristate
 	select REGMAP_SPI
 
+config FXAS21002C
+	tristate "Freescale FXAS21002C Gyroscope"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say yes here to build support for the Freescale FXAS21002C Gyroscope
+	  driver connected via I2C.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called fxas21002c.
+
 config HID_SENSOR_GYRO_3D
 	depends on HID_SENSOR_HUB
 	select IIO_BUFFER
diff --git a/drivers/iio/gyro/Makefile b/drivers/iio/gyro/Makefile
index 295ec780c4eb..ec3e2aeae92a 100644
--- a/drivers/iio/gyro/Makefile
+++ b/drivers/iio/gyro/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_ADXRS450) += adxrs450.o
 obj-$(CONFIG_BMG160) += bmg160_core.o
 obj-$(CONFIG_BMG160_I2C) += bmg160_i2c.o
 obj-$(CONFIG_BMG160_SPI) += bmg160_spi.o
+obj-$(CONFIG_FXAS21002C) += fxas21002c.o
 
 obj-$(CONFIG_HID_SENSOR_GYRO_3D) += hid-sensor-gyro-3d.o
 
diff --git a/drivers/iio/gyro/fxas21002c.c b/drivers/iio/gyro/fxas21002c.c
new file mode 100644
index 000000000000..261b73629544
--- /dev/null
+++ b/drivers/iio/gyro/fxas21002c.c
@@ -0,0 +1,367 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * FXAS21002C - Digital Angular Rate Gyroscope driver
+ *
+ * Copyright (c) 2018, Afonso Bordado <afonsobordado@....co>
+ *
+ * IIO driver for FXAS21002C (7-bit I2C slave address 0x20 or 0x21).
+ * Datasheet: https://www.nxp.com/docs/en/data-sheet/FXAS21002.pdf
+ * TODO:
+ *        ODR / Scale Support
+ *        Devicetree
+ *        Power management
+ *        LowPass/HighPass Filters
+ *        Buffers
+ *        Interrupts
+ *        Alarms
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/regmap.h>
+
+#define FXAS21002C_DRV_NAME "fxas21002c"
+
+#define FXAS21002C_MAX_TRANSITION_TIME_MS 61
+
+#define FXAS21002C_CHIP_ID             0xD7
+
+#define FXAS21002C_REG_STATUS          0x00
+#define FXAS21002C_REG_OUT_X_MSB       0x01
+#define FXAS21002C_REG_OUT_X_LSB       0x02
+#define FXAS21002C_REG_OUT_Y_MSB       0x03
+#define FXAS21002C_REG_OUT_Y_LSB       0x04
+#define FXAS21002C_REG_OUT_Z_MSB       0x05
+#define FXAS21002C_REG_OUT_Z_LSB       0x06
+#define FXAS21002C_REG_DR_STATUS       0x07
+#define FXAS21002C_REG_F_STATUS        0x08
+#define FXAS21002C_REG_F_SETUP         0x09
+#define FXAS21002C_REG_F_EVENT         0x0A
+#define FXAS21002C_REG_INT_SRC_FLAG    0x0B
+#define FXAS21002C_REG_WHO_AM_I        0x0C
+#define FXAS21002C_REG_CTRL_REG0       0x0D
+#define FXAS21002C_REG_RT_CFG          0x0E
+#define FXAS21002C_REG_RT_SRC          0x0F
+#define FXAS21002C_REG_RT_THS          0x10
+#define FXAS21002C_REG_RT_COUNT        0x11
+#define FXAS21002C_REG_TEMP            0x12
+
+#define FXAS21002C_REG_CTRL_REG1       0x13
+#define FXAS21002C_RST_BIT             BIT(6)
+#define FXAS21002C_ACTIVE_BIT          BIT(1)
+#define FXAS21002C_READY_BIT           BIT(0)
+
+#define FXAS21002C_REG_CTRL_REG2       0x14
+#define FXAS21002C_REG_CTRL_REG3       0x15
+
+#define FXAS21002C_DEFAULT_ODR_HZ      800
+
+/* 0.0625 deg/s */
+#define FXAS21002C_DEFAULT_SENSITIVITY IIO_DEGREE_TO_RAD(62500)
+
+#define FXAS21002C_TEMP_SCALE          1000
+
+enum fxas21002c_id {
+	ID_FXAS21002C,
+};
+
+enum fxas21002c_operating_mode {
+	FXAS21002C_OM_BOOT,
+	FXAS21002C_OM_STANDBY,
+	FXAS21002C_OM_READY,
+	FXAS21002C_OM_ACTIVE,
+};
+
+struct fxas21002c_data {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+static const struct regmap_range fxas21002c_writable_ranges[] = {
+	regmap_reg_range(FXAS21002C_REG_F_SETUP, FXAS21002C_REG_F_SETUP),
+	regmap_reg_range(FXAS21002C_REG_CTRL_REG0, FXAS21002C_REG_RT_CFG),
+	regmap_reg_range(FXAS21002C_REG_RT_THS, FXAS21002C_REG_RT_COUNT),
+	regmap_reg_range(FXAS21002C_REG_CTRL_REG1, FXAS21002C_REG_CTRL_REG3),
+};
+
+static const struct regmap_access_table fxas21002c_writable_table = {
+	.yes_ranges = fxas21002c_writable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(fxas21002c_writable_ranges),
+};
+
+static const struct regmap_range fxas21002c_volatile_ranges[] = {
+	regmap_reg_range(FXAS21002C_REG_STATUS, FXAS21002C_REG_F_STATUS),
+	regmap_reg_range(FXAS21002C_REG_F_EVENT, FXAS21002C_REG_INT_SRC_FLAG),
+	regmap_reg_range(FXAS21002C_REG_RT_COUNT, FXAS21002C_REG_CTRL_REG1),
+};
+
+static const struct regmap_access_table fxas21002c_volatile_table = {
+	.yes_ranges = fxas21002c_volatile_ranges,
+	.n_yes_ranges = ARRAY_SIZE(fxas21002c_volatile_ranges),
+};
+
+const struct regmap_config fxas21002c_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = FXAS21002C_REG_CTRL_REG3,
+	/* We don't specify a .rd_table because everything is readable */
+	.wr_table = &fxas21002c_writable_table,
+	.volatile_table = &fxas21002c_volatile_table,
+};
+EXPORT_SYMBOL(fxas21002c_regmap_config);
+
+#define FXAS21002C_GYRO_CHAN(_axis) {					\
+	.type = IIO_ANGL_VEL,						\
+	.modified = 1,							\
+	.channel2 = IIO_MOD_ ## _axis,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
+				    BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
+	.address = FXAS21002C_REG_OUT_ ## _axis ## _MSB,		\
+}
+
+static const struct iio_chan_spec fxas21002c_channels[] = {
+	{
+		.type = IIO_TEMP,
+		.address = FXAS21002C_REG_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	},
+	FXAS21002C_GYRO_CHAN(X),
+	FXAS21002C_GYRO_CHAN(Y),
+	FXAS21002C_GYRO_CHAN(Z),
+	IIO_CHAN_SOFT_TIMESTAMP(3),
+};
+
+static int fxas21002c_set_operating_mode(struct fxas21002c_data *data,
+					 enum fxas21002c_operating_mode om)
+{
+	int ret;
+	int mask;
+
+	switch (om) {
+	case FXAS21002C_OM_STANDBY:
+		mask = 0;
+		break;
+	case FXAS21002C_OM_READY:
+		mask = FXAS21002C_READY_BIT;
+		break;
+	case FXAS21002C_OM_ACTIVE:
+		mask = FXAS21002C_ACTIVE_BIT;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	ret = regmap_write(data->regmap, FXAS21002C_REG_CTRL_REG1, mask);
+	if (ret) {
+		dev_err(&data->client->dev,
+			"could not switch operating mode\n");
+		return ret;
+	}
+
+	msleep(FXAS21002C_MAX_TRANSITION_TIME_MS);
+
+	return 0;
+}
+
+static void fxas21002c_standby(void *_data)
+{
+	struct fxas21002c_data *data = _data;
+
+	fxas21002c_set_operating_mode(data, FXAS21002C_OM_STANDBY);
+}
+
+static int fxas21002c_reset(struct fxas21002c_data *data)
+{
+	int ret;
+
+	/*
+	 * On issuing a Software Reset command over an I2C interface,
+	 * the device immediately resets and does not send any
+	 * acknowledgment (ACK) of the written byte to the Master.
+	 *
+	 * This is documented in table 46 on the datasheet. Due to this
+	 * the write will fail with EREMOTEIO.
+	 */
+	ret = regmap_write(data->regmap,
+			   FXAS21002C_REG_CTRL_REG1, FXAS21002C_RST_BIT);
+
+	if (ret != -EREMOTEIO) {
+		dev_err(&data->client->dev, "could not reset device\n");
+		return ret;
+	}
+
+	regcache_mark_dirty(data->regmap);
+
+	/* Wait for device to boot up */
+	msleep(FXAS21002C_MAX_TRANSITION_TIME_MS);
+
+	return 0;
+}
+
+static int fxas21002c_verify_chip(struct fxas21002c_data *data)
+{
+	int ret;
+	int chip_id;
+
+	ret = regmap_read(data->regmap, FXAS21002C_REG_WHO_AM_I, &chip_id);
+	if (ret) {
+		dev_err(&data->client->dev, "could not read device id\n");
+		return ret;
+	}
+
+	if (chip_id != FXAS21002C_CHIP_ID) {
+		dev_err(&data->client->dev,
+			"unsupported chip id %02x\n", chip_id);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int fxas21002c_read_oneshot(struct fxas21002c_data *data,
+				   struct iio_chan_spec const *chan, int *val)
+{
+	int ret;
+	__be16 bulk_raw;
+
+	switch (chan->type) {
+	case IIO_ANGL_VEL:
+		ret = regmap_bulk_read(data->regmap, chan->address,
+				       &bulk_raw, sizeof(bulk_raw));
+		if (ret)
+			return ret;
+
+		*val = sign_extend32(be16_to_cpu(bulk_raw), 15);
+		return IIO_VAL_INT;
+	case IIO_TEMP:
+		ret = regmap_read(data->regmap, chan->address, val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int fxas21002c_read_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan, int *val,
+			       int *val2, long mask)
+{
+	struct fxas21002c_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return fxas21002c_read_oneshot(data, chan, val);
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_ANGL_VEL:
+			*val = 0;
+			*val2 = FXAS21002C_DEFAULT_SENSITIVITY;
+
+			return IIO_VAL_INT_PLUS_MICRO;
+		case IIO_TEMP:
+			*val = FXAS21002C_TEMP_SCALE;
+
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		if (chan->type != IIO_ANGL_VEL)
+			return -EINVAL;
+
+		*val = FXAS21002C_DEFAULT_ODR_HZ;
+
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info fxas21002c_info = {
+	.read_raw		= fxas21002c_read_raw,
+};
+
+static int fxas21002c_probe(struct i2c_client *client,
+			    const struct i2c_device_id *id)
+{
+	int ret;
+	struct iio_dev *indio_dev;
+	struct fxas21002c_data *data;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, indio_dev);
+	data = iio_priv(indio_dev);
+	data->client = client;
+
+	data->regmap = devm_regmap_init_i2c(client, &fxas21002c_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		ret = PTR_ERR(data->regmap);
+		dev_err(&client->dev,
+			"Failed to allocate regmap, err: %d\n", ret);
+		return ret;
+	}
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->channels = fxas21002c_channels;
+	indio_dev->num_channels = ARRAY_SIZE(fxas21002c_channels);
+	indio_dev->name = id->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &fxas21002c_info;
+
+	ret = fxas21002c_verify_chip(data);
+	if (ret < 0)
+		return ret;
+
+	ret = fxas21002c_reset(data);
+	if (ret < 0)
+		return ret;
+
+	ret = fxas21002c_set_operating_mode(data, FXAS21002C_OM_ACTIVE);
+	if (ret < 0)
+		return ret;
+
+	ret = devm_add_action(&client->dev, fxas21002c_standby, data);
+	if (ret < 0) {
+		fxas21002c_standby(data);
+		dev_err(&client->dev, "failed to add standby action\n");
+		return ret;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0)
+		dev_err(&client->dev, "failed to register iio device\n");
+
+	return ret;
+}
+
+static const struct i2c_device_id fxas21002c_id[] = {
+	{"fxas21002c", ID_FXAS21002C},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, fxas21002c_id);
+
+static struct i2c_driver fxas21002c_driver = {
+	.driver = {
+		.name = FXAS21002C_DRV_NAME,
+	},
+	.probe		= fxas21002c_probe,
+	.id_table	= fxas21002c_id,
+};
+
+module_i2c_driver(fxas21002c_driver);
+
+MODULE_AUTHOR("Afonso Bordado <afonsobordado@....co>");
+MODULE_DESCRIPTION("FXAS21002C Digital Angular Rate Gyroscope driver");
+MODULE_LICENSE("GPL v2");
-- 
2.18.0


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