Message-ID: <20210418130835.26a63bdb@jic23-huawei>
Date:   Sun, 18 Apr 2021 13:08:35 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Tomas Melin <tomas.melin@...sala.com>
Cc:     devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: accel: Add driver for Murata SCA3300
 accelerometer

On Fri, 16 Apr 2021 16:45:46 +0300
Tomas Melin <tomas.melin@...sala.com> wrote:

> Add initial support for Murata SCA3300 3-axis industrial
> accelerometer with digital SPI interface. This device also
> provides a temperature measurement.
> 
> Device product page including datasheet can be found at:
> https://www.murata.com/en-global/products/sensor/accel/sca3300
> 
> Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
A few things inline.  Mostly looks pretty good

Jonathan

> ---
>  drivers/iio/accel/Kconfig   |  13 +
>  drivers/iio/accel/Makefile  |   1 +
>  drivers/iio/accel/sca3300.c | 468 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 482 insertions(+)
>  create mode 100644 drivers/iio/accel/sca3300.c
> 
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index cceda3cecbcf..0dbf7b648e8a 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -450,6 +450,19 @@ config SCA3000
>  	  To compile this driver as a module, say M here: the module will be
>  	  called sca3000.
>  
> +config SCA3300
> +	tristate "Murata SCA3300 3-Axis Accelerometer Driver"
> +	depends on SPI
> +	select CRC8
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  Say yes here to build support for Murata SCA3300 3-Axis
> +	  accelerometer.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called sca3300.
> +
>  config STK8312
>  	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
>  	depends on I2C
> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> index 32cd1342a31a..4b56527a2b97 100644
> --- a/drivers/iio/accel/Makefile
> +++ b/drivers/iio/accel/Makefile
> @@ -50,6 +50,7 @@ obj-$(CONFIG_MXC4005)		+= mxc4005.o
>  obj-$(CONFIG_MXC6255)		+= mxc6255.o
>  
>  obj-$(CONFIG_SCA3000)		+= sca3000.o
> +obj-$(CONFIG_SCA3300)		+= sca3300.o
>  
>  obj-$(CONFIG_STK8312)		+= stk8312.o
>  obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
> diff --git a/drivers/iio/accel/sca3300.c b/drivers/iio/accel/sca3300.c
> new file mode 100644
> index 000000000000..79c3c60f9fab
> --- /dev/null
> +++ b/drivers/iio/accel/sca3300.c
> @@ -0,0 +1,468 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2021 Vaisala Oyj. All rights reserved.
> + */
> +#include <asm/unaligned.h>

Slight preference for 'specific' includes such asm after the generic
linux ones.

> +#include <linux/bitops.h>
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +
> +#define SCA3300_ALIAS "sca3300"
> +
> +#define SCA3300_REG_STATUS 0x6
> +#define SCA3300_REG_MODE 0xd
> +#define SCA3300_REG_WHOAMI 0x10
> +#define SCA3300_VALUE_SW_RESET 0x20
> +#define SCA3300_CRC8_POLYNOMIAL 0x1d
> +#define SCA3300_DEVICE_ID 0x51
> +#define SCA3300_RS_ERROR 0x3
> +#define SCA3300_SELBANK 0x1f
> +#define SCA3300_STATUS_MASK 0x1ff
> +
> +enum sca3300_scan_indexes {
> +	SCA3300_ACC_X = 0,
> +	SCA3300_ACC_Y,
> +	SCA3300_ACC_Z,
> +	SCA3300_TEMP,
> +	SCA3300_TIMESTAMP,
> +};
> +
> +#define SCA3300_ACCEL_CHANNEL(index, reg, axis) {			\
> +		.type = IIO_ACCEL,					\
> +			.address = reg,					\
> +			.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_LOW_PASS_FILTER_3DB_FREQUENCY), \
> +			.info_mask_shared_by_type_available = \
> +			BIT(IIO_CHAN_INFO_SCALE) | \
> +			BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY), \
> +			.scan_index = index,				\
> +			.scan_type = {					\
> +			.sign = 's',					\
> +			.realbits = 16,					\
> +			.storagebits = 16,				\
> +			.shift = 0,					\
> +			.endianness = IIO_CPU,				\
> +		},							\
> +			}

Alignment done something odd here and above. Editors get confused by
macros so you might need to tweak this carefully!

> +
> +static const struct iio_chan_spec sca3300_channels[] = {
> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_X, 0x1, X),
> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_Y, 0x2, Y),
> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_Z, 0x3, Z),
> +	{
> +		.type = IIO_TEMP,
> +		.address = 0x5,
> +		.scan_index = SCA3300_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 16,
> +			.storagebits = 16,
> +			.shift = 0,

Obviously default, so no need to specify a shift of 0.

> +			.endianness = IIO_CPU,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(4),
> +};
> +
> +static const int sca3300_lp_freq[] = {70, 70, 70, 10};
> +static const int sca3300_accel_scale[][2] = {{0, 370}, {0, 741}, {0, 185},
> +					    {0, 185}};
> +
> +static const unsigned long sca3300_scan_masks[] = {
> +	BIT(SCA3300_ACC_X) | BIT(SCA3300_ACC_Y) | BIT(SCA3300_ACC_Z) |
> +	BIT(SCA3300_TEMP),
> +	0};
> +
> +/**
> + * struct sca3300_data - device data
> + * @spi: SPI device structure
> + * @lock: Data buffer lock
> + * @txbuf: Transmit buffer
> + * @rxbuf: Receive buffer
> + * @scan: Triggered buffer. Four channel 16-bit data + 64-bit timestamp
> + */
> +struct sca3300_data {
> +	struct spi_device *spi;
> +	struct mutex lock;
> +	u8 txbuf[4];
> +	u8 rxbuf[4];
> +	struct {
> +		s16 channels[4];
> +		s64 ts __aligned(sizeof(s64));
> +	} scan;
> +};
> +
> +DECLARE_CRC8_TABLE(sca3300_crc_table);
> +
> +static int sca3300_transfer(struct sca3300_data *sca_data, int *val)
> +{
> +	struct spi_delay delay = {.value = 10, .unit = SPI_DELAY_UNIT_USECS};
> +	int32_t ret;
> +	int rs;
> +	u8 crc;
> +	struct spi_transfer xfers[2] = {
> +		{
> +			.tx_buf = sca_data->txbuf,
> +			.rx_buf = NULL,
> +			.len = ARRAY_SIZE(sca_data->txbuf),
> +			.delay = delay,
> +			.cs_change = 1,
> +		},
> +		{
> +			.tx_buf = NULL,

Obvious default, don't bother specifying these buffers are NULL.

> +			.rx_buf = sca_data->rxbuf,
> +			.len = ARRAY_SIZE(sca_data->rxbuf),
> +			.delay = delay,
> +			.cs_change = 0,

That should be obvious default, so don't bother specifying it.

> +		}
> +	};
> +
> +	/* inverted crc value as described in device data sheet */
> +	crc = ~crc8(sca3300_crc_table, &sca_data->txbuf[0], 3, CRC8_INIT_VALUE);
> +	sca_data->txbuf[3] = crc;
> +
> +	ret = spi_sync_transfer(sca_data->spi, xfers, ARRAY_SIZE(xfers));
> +	if (ret < 0) {
> +		dev_err(&sca_data->spi->dev,
> +			"transfer error, error: %d\n", ret);
> +		return -EIO;
> +	}
> +
> +	crc = ~crc8(sca3300_crc_table, &sca_data->rxbuf[0], 3, CRC8_INIT_VALUE);
> +	if (sca_data->rxbuf[3] != crc) {
> +		dev_err(&sca_data->spi->dev, "CRC checksum mismatch");
> +		return -EIO;
> +	}
> +
> +	/* get return status */
> +	rs = sca_data->rxbuf[0] & 0x03;
> +	if (rs == SCA3300_RS_ERROR)
> +		ret = -EINVAL;
> +
> +	*val = sign_extend32(get_unaligned_be16(&sca_data->rxbuf[1]), 15);
> +
> +	return ret;
> +}
> +
> +static int sca3300_error_handler(struct sca3300_data *sca_data)
> +{
> +	int ret;
> +	int val;
> +
> +	mutex_lock(&sca_data->lock);
> +	sca_data->txbuf[0] = 0x0 | (SCA3300_REG_STATUS << 2);
> +	ret = sca3300_transfer(sca_data, &val);
> +	mutex_unlock(&sca_data->lock);
> +	/* return status is cleared after reading status register */
> +	if (ret != -EINVAL) {
> +		dev_err(&sca_data->spi->dev,
> +			"error reading device status: %d\n", ret);
> +		return ret;
> +	}
> +
> +	dev_err(&sca_data->spi->dev, "device status: 0x%x\n",
> +		(u16)(val & SCA3300_STATUS_MASK));

Why the cast? Not sure it does anything useful.

> +	return 0;
> +}
> +
> +static int sca3300_read_reg(struct sca3300_data *sca_data, u8 reg, int *val)
> +{
> +	int ret;
> +
> +	mutex_lock(&sca_data->lock);
> +	sca_data->txbuf[0] = 0x0 | (reg << 2);
> +	ret = sca3300_transfer(sca_data, val);
> +	mutex_unlock(&sca_data->lock);
> +	if (ret == -EINVAL)
> +		ret  = sca3300_error_handler(sca_data);
> +
> +	return ret;
> +}
> +
> +static int sca3300_write_reg(struct sca3300_data *sca_data, u8 reg, int val)
> +{
> +	int reg_val = 0;
> +	int ret;
> +
> +	mutex_lock(&sca_data->lock);
> +	sca_data->txbuf[0] = BIT(7) | (reg << 2);
> +	put_unaligned_be16(val, &sca_data->txbuf[1]);
> +	ret = sca3300_transfer(sca_data, &reg_val);
> +	mutex_unlock(&sca_data->lock);
> +	if (ret == -EINVAL)
> +		ret  = sca3300_error_handler(sca_data);
> +
> +	return ret;
> +}
> +
> +static int sca3300_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct sca3300_data *data = iio_priv(indio_dev);
> +	int reg_val;
> +	int ret;
> +	int i;
> +	int idx = -1;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		if (val)
> +			return -EINVAL;
> +
> +		for (i = 0; i < ARRAY_SIZE(sca3300_accel_scale); i++) {
> +			if (val2 == sca3300_accel_scale[i][1]) {
> +				idx = i;
> +				break;
> +			}
> +		}
> +		if (idx == -1)
> +			return -EINVAL;
> +
> +		return sca3300_write_reg(data, SCA3300_REG_MODE, idx);
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		ret = sca3300_read_reg(data, SCA3300_REG_MODE, &reg_val);
> +		if (ret < 0)
> +			return ret;
> +		/* freq. change is possible only for mode 3 and 4 */
> +		if (reg_val == 2 && val == sca3300_lp_freq[3])
> +			return sca3300_write_reg(data, SCA3300_REG_MODE, 3);
> +		else if (reg_val == 3 && val == sca3300_lp_freq[2])
> +			return sca3300_write_reg(data, SCA3300_REG_MODE, 2);
> +		else
> +			return -EINVAL;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int sca3300_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct sca3300_data *data = iio_priv(indio_dev);
> +	int ret;
> +	int reg_val;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = sca3300_read_reg(data, chan->address, val);
> +		if (ret < 0)
> +			return ret;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = sca3300_read_reg(data, SCA3300_REG_MODE, &reg_val);
> +		if (ret < 0)
> +			return ret;
> +		*val = 0;
> +		*val2 = sca3300_accel_scale[reg_val][1];
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		ret = sca3300_read_reg(data, SCA3300_REG_MODE, &reg_val);
> +		if (ret < 0)
> +			return ret;
> +		*val = sca3300_lp_freq[reg_val];
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static irqreturn_t sca3300_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct sca3300_data *data = iio_priv(indio_dev);
> +	int bit, ret, val, i = 0;
> +
> +	for_each_set_bit(bit, indio_dev->active_scan_mask,
> +			 indio_dev->masklength) {
> +		ret = sca3300_read_reg(data, sca3300_channels[bit].address,
> +				       &val);
> +		if (ret < 0) {
> +			dev_err(&data->spi->dev,
> +				"failed to read register, error: %d\n", ret);
> +			goto out;
> +		}
> +		((s16 *)data->scan.channels)[i++] = val;

Why do you need the cast?

> +	}
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
> +					   iio_get_time_ns(indio_dev));
> +out:
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*
> + * sca3300_init - Device init sequence. See datasheet rev 2 section
> + * 4.2 Start-Up Sequence for details.
> + */
> +static int sca3300_init(struct sca3300_data *sca_data,
> +			struct iio_dev *indio_dev)
> +{
> +	int ret;
> +	int value = 0;
> +
> +	ret = sca3300_write_reg(sca_data, SCA3300_REG_MODE,
> +				SCA3300_VALUE_SW_RESET);
> +	if (ret != 0)
> +		return ret;
> +	/* wait at least 1ms after SW-reset command */
> +	usleep_range(1e3, 10e3);
> +
> +	/* wait 15ms for settling of signal paths */
> +	usleep_range(15e3, 50e3);
> +	ret = sca3300_read_reg(sca_data, SCA3300_REG_WHOAMI, &value);
> +	if (ret != 0)

For error checks we tend to just use
	if (ret)

Same in a few other places.

> +		return ret;
> +
> +	if (value != SCA3300_DEVICE_ID) {
> +		dev_err(&sca_data->spi->dev,
> +			"device id not expected value, %d != %u\n",
> +			value, SCA3300_DEVICE_ID);
> +		return -EIO;
> +	}
> +	return 0;
> +}
> +
> +static int sca3300_debugfs_reg_access(struct iio_dev *indio_dev,
> +				      unsigned int reg, unsigned int writeval,
> +				      unsigned int *readval)
> +{
> +	struct sca3300_data *data = iio_priv(indio_dev);
> +	int value;
> +	int ret;
> +
> +	if (reg > SCA3300_SELBANK)
> +		return -EINVAL;
> +
> +	if (!readval)
> +		return sca3300_write_reg(data, reg, writeval);
> +
> +	ret = sca3300_read_reg(data, reg, &value);
> +	if (ret < 0)
> +		return ret;
> +
> +	*readval = (unsigned int)value;
> +
> +	return 0;
> +}
> +
> +static int sca3300_read_avail(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan,
> +			      const int **vals,

You could wrap this a little less without hurting readability I think.

> +			      int *type,
> +			      int *length,
> +			      long mask)
> +{
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		*vals = (const int *)sca3300_accel_scale;
> +		*length = ARRAY_SIZE(sca3300_accel_scale) * 2 - 2;
> +		*type = IIO_VAL_INT_PLUS_MICRO;
> +		return IIO_AVAIL_LIST;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		*vals = &sca3300_lp_freq[2];
> +		*length = 2;
> +		*type = IIO_VAL_INT;
> +		return IIO_AVAIL_LIST;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info sca3300_info = {
> +	.read_raw = sca3300_read_raw,
> +	.write_raw = sca3300_write_raw,
> +	.debugfs_reg_access = &sca3300_debugfs_reg_access,
> +	.read_avail = sca3300_read_avail,
> +};
> +
> +static int sca3300_probe(struct spi_device *spi)
> +{
> +	struct sca3300_data *sca_data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*sca_data));
> +	if (!indio_dev) {
> +		dev_err(&spi->dev,
> +			"failed to allocate memory for iio device\n");
> +		return -ENOMEM;
> +	}
> +
> +	sca_data = iio_priv(indio_dev);
> +	mutex_init(&sca_data->lock);
> +	sca_data->spi = spi;
> +
> +	crc8_populate_msb(sca3300_crc_table, SCA3300_CRC8_POLYNOMIAL);
> +
> +	indio_dev->dev.parent = &spi->dev;

This should now be set by the IIO core IIRC.

> +	indio_dev->info = &sca3300_info;
> +	indio_dev->name = SCA3300_ALIAS;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = sca3300_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(sca3300_channels);
> +	indio_dev->available_scan_masks = sca3300_scan_masks;
> +
> +	ret = sca3300_init(sca_data, indio_dev);
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "failed to init device, error: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
> +					      iio_pollfunc_store_time,
> +					      sca3300_trigger_handler, NULL);
> +	if (ret < 0) {
> +		dev_err(&spi->dev,
> +			"iio triggered buffer setup failed, error: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = devm_iio_device_register(&spi->dev, indio_dev);
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "iio device register failed, error: %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id sca3300_dt_ids[] = {
> +	{ .compatible = "murata,sca3300"},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, sca3300_dt_ids);
> +
> +static struct spi_driver sca3300_driver = {
> +	.driver = {
> +		.name		= SCA3300_ALIAS,
> +		.owner		= THIS_MODULE,
> +		.of_match_table = of_match_ptr(sca3300_dt_ids),
> +	},
> +
> +	.probe	= sca3300_probe,
> +};
> +
> +module_spi_driver(sca3300_driver);
> +
> +MODULE_AUTHOR("Tomas Melin <tomas.melin@...sala.com>");
> +MODULE_DESCRIPTION("Murata SCA3300 SPI Accelerometer");
> +MODULE_LICENSE("GPL v2");

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