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Date:   Sat, 8 Dec 2018 15:55:26 +0000
From:   Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
To:     Tomasz Duszynski <tduszyns@gmail.com>
Cc:     linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, robh+dt@kernel.org,
        a.brauchli@elementarea.net
Subject: Re: [PATCH v2 2/3] iio: chemical: add support for Sensirion SPS30
 sensor
Message-ID: <20181208155526.5b0a563f@archlinux>
In-Reply-To: <20181206210443.21052-3-tduszyns@gmail.com>
References: <20181206210443.21052-1-tduszyns@gmail.com>
        <20181206210443.21052-3-tduszyns@gmail.com>
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On Thu,  6 Dec 2018 22:04:42 +0100
Tomasz Duszynski <tduszyns@gmail.com> wrote:

> Add support for Sensirion SPS30 particulate matter sensor.
> 
> Signed-off-by: Tomasz Duszynski <tduszyns@gmail.com>

Just one comment inline and if that is all anyone comes up with
I'll take it as it stands and we can tidy that up whenever we get
around to it.

So, as with patch 1, I'd like to let this sit for a few days to
give others time to take a look at V2.

Thanks,

Jonathan

> ---
>  drivers/iio/chemical/Kconfig  |  11 +
>  drivers/iio/chemical/Makefile |   1 +
>  drivers/iio/chemical/sps30.c  | 406 ++++++++++++++++++++++++++++++++++
>  3 files changed, 418 insertions(+)
>  create mode 100644 drivers/iio/chemical/sps30.c
> 
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index b8e005be4f87..57832b4360e9 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -61,6 +61,17 @@ config IAQCORE
>  	  iAQ-Core Continuous/Pulsed VOC (Volatile Organic Compounds)
>  	  sensors
>  
> +config SPS30
> +	tristate "SPS30 particulate matter sensor"
> +	depends on I2C
> +	select CRC8
> +	help
> +	  Say Y here to build support for the Sensirion SPS30 particulate
> +	  matter sensor.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called sps30.
> +
>  config VZ89X
>  	tristate "SGX Sensortech MiCS VZ89X VOC sensor"
>  	depends on I2C
> diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> index 2f4c4ba4d781..9f42f4252151 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -9,4 +9,5 @@ obj-$(CONFIG_BME680_I2C) += bme680_i2c.o
>  obj-$(CONFIG_BME680_SPI) += bme680_spi.o
>  obj-$(CONFIG_CCS811)		+= ccs811.o
>  obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
> +obj-$(CONFIG_SPS30) += sps30.o
>  obj-$(CONFIG_VZ89X)		+= vz89x.o
> diff --git a/drivers/iio/chemical/sps30.c b/drivers/iio/chemical/sps30.c
> new file mode 100644
> index 000000000000..4857b6164dd2
> --- /dev/null
> +++ b/drivers/iio/chemical/sps30.c
> @@ -0,0 +1,406 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sensirion SPS30 Particulate Matter sensor driver
> + *
> + * Copyright (c) Tomasz Duszynski <tduszyns@gmail.com>
> + *
> + * I2C slave address: 0x69
> + *
> + * TODO:
> + *  - support for turning on fan cleaning
> + *  - support for reading/setting auto cleaning interval
> + */
> +
> +#define pr_fmt(fmt) "sps30: " fmt
> +
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.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/module.h>
> +
> +#define SPS30_CRC8_POLYNOMIAL 0x31
> +/* max number of bytes needed to store PM measurements or serial string */
> +#define SPS30_MAX_READ_SIZE 48
> +/* sensor measures reliably up to 3000 ug / m3 */
> +#define SPS30_MAX_PM 3000
> +
> +/* SPS30 commands */
> +#define SPS30_START_MEAS 0x0010
> +#define SPS30_STOP_MEAS 0x0104
> +#define SPS30_RESET 0xd304
> +#define SPS30_READ_DATA_READY_FLAG 0x0202
> +#define SPS30_READ_DATA 0x0300
> +#define SPS30_READ_SERIAL 0xd033
> +
> +enum {
> +	PM1,
> +	PM2P5,
> +	PM4,
> +	PM10,
> +};
> +
> +struct sps30_state {
> +	struct i2c_client *client;
> +	/*
> +	 * Guards against concurrent access to sensor registers.
> +	 * Must be held whenever sequence of commands is to be executed.
> +	 */
> +	struct mutex lock;
> +};
> +
> +DECLARE_CRC8_TABLE(sps30_crc8_table);
> +
> +static int sps30_write_then_read(struct sps30_state *state, u8 *txbuf,
> +				 int txsize, u8 *rxbuf, int rxsize)
> +{
> +	int ret;
> +
> +	/*
> +	 * Sensor does not support repeated start so instead of
> +	 * sending two i2c messages in a row we just send one by one.
> +	 */
> +	ret = i2c_master_send(state->client, txbuf, txsize);
> +	if (ret != txsize)
> +		return ret < 0 ? ret : -EIO;
> +
> +	if (!rxbuf)
> +		return 0;
> +
> +	ret = i2c_master_recv(state->client, rxbuf, rxsize);
> +	if (ret != rxsize)
> +		return ret < 0 ? ret : -EIO;
> +
> +	return 0;
> +}
> +
> +static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
> +{
> +	/*
> +	 * Internally sensor stores measurements in a following manner:
> +	 *
> +	 * PM1: upper two bytes, crc8, lower two bytes, crc8
> +	 * PM2P5: upper two bytes, crc8, lower two bytes, crc8
> +	 * PM4: upper two bytes, crc8, lower two bytes, crc8
> +	 * PM10: upper two bytes, crc8, lower two bytes, crc8
> +	 *
> +	 * What follows next are number concentration measurements and
> +	 * typical particle size measurement which we omit.
> +	 */
> +	u8 buf[SPS30_MAX_READ_SIZE] = { cmd >> 8, cmd };
> +	int i, ret = 0;
> +
> +	switch (cmd) {
> +	case SPS30_START_MEAS:
> +		buf[2] = 0x03;
> +		buf[3] = 0x00;
> +		buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
> +		ret = sps30_write_then_read(state, buf, 5, NULL, 0);
> +		break;
> +	case SPS30_STOP_MEAS:
> +	case SPS30_RESET:
> +		ret = sps30_write_then_read(state, buf, 2, NULL, 0);
> +		break;
> +	case SPS30_READ_DATA_READY_FLAG:
> +	case SPS30_READ_DATA:
> +	case SPS30_READ_SERIAL:
> +		/* every two data bytes are checksummed */
> +		size += size / 2;
> +		ret = sps30_write_then_read(state, buf, 2, buf, size);
> +		break;
> +	};
> +
> +	if (ret)
> +		return ret;
> +
> +	/* validate received data and strip off crc bytes */
> +	for (i = 0; i < size; i += 3) {
> +		u8 crc = crc8(sps30_crc8_table, &buf[i], 2, CRC8_INIT_VALUE);
> +
> +		if (crc != buf[i + 2]) {
> +			dev_err(&state->client->dev,
> +				"data integrity check failed\n");
> +			return -EIO;
> +		}
> +
> +		*data++ = buf[i];
> +		*data++ = buf[i + 1];
> +	}
> +
> +	return 0;
> +}
> +
> +static int sps30_float_to_int_clamped(const u8 *fp)
> +{
> +	int val = ((int)fp[0] << 24) | ((int)fp[1] << 16) | ((int)fp[2] << 8) |
> +		  (int)fp[3];

This is to convert from big endian 32bit to cpu endian.  Please use

be32_to_cpu as that means it's free on a big endian system.
(I think I have that the right way around!)

> +	int mantissa = val & GENMASK(22, 0);
> +	/* this is fine since passed float is always non-negative */
> +	int exp = val >> 23;
> +	int fraction, shift;
> +
> +	/* special case 0 */
> +	if (!exp && !mantissa)
> +		return 0;
> +
> +	exp -= 127;
> +	if (exp < 0) {
> +		/* return values ranging from 1 to 99 */
> +		return ((((1 << 23) + mantissa) * 100) >> 23) >> (-exp);
> +	}
> +
> +	/* return values ranging from 100 to 300000 */
> +	shift = 23 - exp;
> +	val = (1 << exp) + (mantissa >> shift);
> +	if (val >= SPS30_MAX_PM)
> +		return SPS30_MAX_PM * 100;
> +
> +	fraction = mantissa & GENMASK(shift - 1, 0);
> +
> +	return val * 100 + ((fraction * 100) >> shift);
> +}
> +
> +static int sps30_do_meas(struct sps30_state *state, int *data, int size)
> +{
> +	int i, ret, tries = 5;
> +	u8 tmp[16];
> +
> +	while (tries--) {
> +		ret = sps30_do_cmd(state, SPS30_READ_DATA_READY_FLAG, tmp, 2);
> +		if (ret)
> +			return -EIO;
> +
> +		/* new measurements ready to be read */
> +		if (tmp[1] == 1)
> +			break;
> +
> +		msleep_interruptible(300);
> +	}
> +
> +	if (!tries)
> +		return -ETIMEDOUT;
> +
> +	ret = sps30_do_cmd(state, SPS30_READ_DATA, tmp, sizeof(int) * size);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < size; i++)
> +		data[i] = sps30_float_to_int_clamped(&tmp[4 * i]);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t sps30_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct sps30_state *state = iio_priv(indio_dev);
> +	int ret, data[4 + 2]; /* PM1, PM2P5, PM4, PM10, timestamp */
> +
> +	mutex_lock(&state->lock);
> +	ret = sps30_do_meas(state, data, 4);
> +	mutex_unlock(&state->lock);
> +	if (ret)
> +		goto err;
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, data,
> +					   iio_get_time_ns(indio_dev));
> +err:
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int sps30_read_raw(struct iio_dev *indio_dev,
> +			  struct iio_chan_spec const *chan,
> +			  int *val, int *val2, long mask)
> +{
> +	struct sps30_state *state = iio_priv(indio_dev);
> +	int data[4], ret = -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		switch (chan->type) {
> +		case IIO_MASSCONCENTRATION:
> +			mutex_lock(&state->lock);
> +			/* read up to the number of bytes actually needed */
> +			switch (chan->channel2) {
> +			case IIO_MOD_PM1:
> +				ret = sps30_do_meas(state, data, 1);
> +				break;
> +			case IIO_MOD_PM2P5:
> +				ret = sps30_do_meas(state, data, 2);
> +				break;
> +			case IIO_MOD_PM4:
> +				ret = sps30_do_meas(state, data, 3);
> +				break;
> +			case IIO_MOD_PM10:
> +				ret = sps30_do_meas(state, data, 4);
> +				break;
> +			}
> +			mutex_unlock(&state->lock);
> +			if (ret)
> +				return ret;
> +
> +			*val = data[chan->address] / 100;
> +			*val2 = (data[chan->address] % 100) * 10000;
> +
> +			return IIO_VAL_INT_PLUS_MICRO;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_MASSCONCENTRATION:
> +			switch (chan->channel2) {
> +			case IIO_MOD_PM1:
> +			case IIO_MOD_PM2P5:
> +			case IIO_MOD_PM4:
> +			case IIO_MOD_PM10:
> +				*val = 0;
> +				*val2 = 10000;
> +
> +				return IIO_VAL_INT_PLUS_MICRO;
> +			}
> +		default:
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info sps30_info = {
> +	.read_raw = sps30_read_raw,
> +};
> +
> +#define SPS30_CHAN(_index, _mod) { \
> +	.type = IIO_MASSCONCENTRATION, \
> +	.modified = 1, \
> +	.channel2 = IIO_MOD_ ## _mod, \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +	.address = _mod, \
> +	.scan_index = _index, \
> +	.scan_type = { \
> +		.sign = 'u', \
> +		.realbits = 19, \
> +		.storagebits = 32, \
> +		.endianness = IIO_CPU, \
> +	}, \
> +}
> +
> +static const struct iio_chan_spec sps30_channels[] = {
> +	SPS30_CHAN(0, PM1),
> +	SPS30_CHAN(1, PM2P5),
> +	SPS30_CHAN(2, PM4),
> +	SPS30_CHAN(3, PM10),
> +	IIO_CHAN_SOFT_TIMESTAMP(4),
> +};
> +
> +static void sps30_stop_meas(void *data)
> +{
> +	struct sps30_state *state = data;
> +
> +	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
> +}
> +
> +static const unsigned long sps30_scan_masks[] = { 0x0f, 0x00 };
> +
> +static int sps30_probe(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev;
> +	struct sps30_state *state;
> +	u8 buf[32];
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> +		return -EOPNOTSUPP;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*state));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	state = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	state->client = client;
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &sps30_info;
> +	indio_dev->name = client->name;
> +	indio_dev->channels = sps30_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(sps30_channels);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->available_scan_masks = sps30_scan_masks;
> +
> +	mutex_init(&state->lock);
> +	crc8_populate_msb(sps30_crc8_table, SPS30_CRC8_POLYNOMIAL);
> +
> +	ret = sps30_do_cmd(state, SPS30_RESET, NULL, 0);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to reset device\n");
> +		return ret;
> +	}
> +	msleep(300);
> +	/*
> +	 * Power-on-reset causes sensor to produce some glitch on i2c bus and
> +	 * some controllers end up in error state. Recover simply by placing
> +	 * some data on the bus, for example STOP_MEAS command, which
> +	 * is NOP in this case.
> +	 */
> +	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
> +
> +	ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
> +	if (ret) {
> +		dev_err(&client->dev, "failed to read serial number\n");
> +		return ret;
> +	}
> +	/* returned serial number is already NUL terminated */
> +	dev_info(&client->dev, "serial number: %s\n", buf);
> +
> +	ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to start measurement\n");
> +		return ret;
> +	}
> +
> +	ret = devm_add_action_or_reset(&client->dev, sps30_stop_meas, state);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
> +					      sps30_trigger_handler, NULL);
> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id sps30_id[] = {
> +	{ "sps30" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, sps30_id);
> +
> +static const struct of_device_id sps30_of_match[] = {
> +	{ .compatible = "sensirion,sps30" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, sps30_of_match);
> +
> +static struct i2c_driver sps30_driver = {
> +	.driver = {
> +		.name = "sps30",
> +		.of_match_table = sps30_of_match,
> +	},
> +	.id_table = sps30_id,
> +	.probe_new = sps30_probe,
> +};
> +module_i2c_driver(sps30_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tduszyns@gmail.com>");
> +MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
> +MODULE_LICENSE("GPL v2");