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Date:   Mon, 27 Aug 2018 18:08:05 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Afonso Bordado <afonsobordado@az8.co>
Cc:     knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH 1/4] iio: gyro: add support for fxas21002c
Message-ID: <20180827180805.7d4b9f4e@archlinux>
In-Reply-To: <20180825211910.22929-1-afonsobordado@az8.co>
References: <20180825211910.22929-1-afonsobordado@az8.co>
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On Sat, 25 Aug 2018 22:19:07 +0100
Afonso Bordado <afonsobordado@az8.co> wrote:

> FXAS21002C is a 3 axis gyroscope with integrated temperature sensor
> 
> Signed-off-by: Afonso Bordado <afonsobordado@az8.co>

Hi,

Driver is pretty clean so only a few minor comments inline.
If we were late in a cycle I'd probably just have taken it and fixed up
but as we have lots of time and I'm inherently lazy I'll let you do a v2 :)

Good job, thanks!

Jonathan


> ---
>  drivers/iio/gyro/Kconfig      |  11 ++
>  drivers/iio/gyro/Makefile     |   1 +
>  drivers/iio/gyro/fxas21002c.c | 363 ++++++++++++++++++++++++++++++++++
>  3 files changed, 375 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..7626b2f88d72
> --- /dev/null
> +++ b/drivers/iio/gyro/fxas21002c.c
> @@ -0,0 +1,363 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * FXAS21002C - Digital Angular Rate Gyroscope driver
> + *
> + * Copyright (c) 2018, Afonso Bordado <afonsobordado@az8.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)
> +
> +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
/* ... */

Please run checkpatch as IIRC it complains about this.

> +	.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),

As it currently stands it is IIO_CHAN_PROCESSED but I'd prefer you provided
the scale and kept it as _RAW.

> +	},
> +	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 = 0;
Might be clearer to not set this here and...
> +
> +	switch (om) {
> +	case FXAS21002C_OM_STANDBY:
		mask = 0;
> +		break;
> +	case FXAS21002C_OM_READY:
> +		mask |= FXAS21002C_READY_BIT;
		mask = FXA210002C_READY_BIT;
> +		break;
> +	case FXAS21002C_OM_ACTIVE:
> +		mask |= FXAS21002C_ACTIVE_BIT;
		mask = FXA21002C_ACTIVE_BIT;

Slightly more readable I think...
> +		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 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

/* Wait... */

> +	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;
> +	int raw;
> +	__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);
> +		break;

return IIO_VAL_INT directly here.

> +	case IIO_TEMP:
> +		ret = regmap_read(data->regmap, chan->address, &raw);
> +		if (ret)
> +			return ret;
> +
> +		*val = raw * 1000; // Convert to millicelsius

Don't use c++ style comments in kernel code please.

Also I wouldn't do this multiplier in here, I'd provide the scale attribute.
The reason is that we may later have support for buffered reads from this
device - at that point we will want to have nice 8 bit data rather than having
a scaled value that isn't quite a whole number of bits.


> +		break;
return IIO_VAL_INT; directly here.
> +	default:
> +		return -EINVAL;
> +	}
> +

With the above two changes in place this return is never reached.

> +	return IIO_VAL_INT;
> +}
> +
> +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:
> +		if (chan->type != IIO_ANGL_VEL)
> +			return -EINVAL;
This check is a bit over paranoid given there is no way
this would be called in with a different type.

Doesn't do any real harm though.

> +
> +		*val = 0;
> +		*val2 = FXAS21002C_DEFAULT_SENSITIVITY;
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	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 = iio_device_register(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to register iio device\n");
> +		fxas21002c_set_operating_mode(data, FXAS21002C_OM_STANDBY);
> +		return ret;

We may potentially get a patch as one of the static analysis tools will point
out that return ret could be dropped out of the brackets without changing the
code (ret is 0 in this case as iio_device_register never returns positive)

Really minor though!

> +	}
> +
> +	return 0;
> +}
> +
> +static int fxas21002c_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct fxas21002c_data *data = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	fxas21002c_set_operating_mode(data, FXAS21002C_OM_STANDBY);
You could have used the devm_add_action to allow the managed cleanup to handle
this and hence gotten rid of the remove function.

(minor suggestion and somewhat a matter of personal taste).

> +
> +	return 0;
> +}
> +
> +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,
> +	.remove		= fxas21002c_remove,
> +	.id_table	= fxas21002c_id,
> +};
> +
> +module_i2c_driver(fxas21002c_driver);
> +
> +MODULE_AUTHOR("Afonso Bordado <afonsobordado@az8.co>");
> +MODULE_DESCRIPTION("FXAS21002C Digital Angular Rate Gyroscope driver");
> +MODULE_LICENSE("GPL v2");