Date:   Sat, 8 Dec 2018 21:09:20 +0100
From:   Tomasz Duszynski <tduszyns@...il.com>
To:     Jonathan Cameron <jic23@...23.retrosnub.co.uk>
Cc:     Tomasz Duszynski <tduszyns@...il.com>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, a.brauchli@...mentarea.net
Subject: Re: [PATCH v2 2/3] iio: chemical: add support for Sensirion SPS30
 sensor

On Sat, Dec 08, 2018 at 03:55:26PM +0000, Jonathan Cameron wrote:
> On Thu,  6 Dec 2018 22:04:42 +0100
> Tomasz Duszynski <tduszyns@...il.com> wrote:
>
> > Add support for Sensirion SPS30 particulate matter sensor.
> >
> > Signed-off-by: Tomasz Duszynski <tduszyns@...il.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.
>

Good. Two things from my side inline, which could be put into separate
patch and squashed once applying this one (in case you're okay with that).

> 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
> > + *

Looks I forgot to change 'Particulate Matter' to lower case here.

> > + * Copyright (c) Tomasz Duszynski <tduszyns@...il.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!)
>

get_unaligned_be32 may work even better in this case as be32_to_cpu
could cause unaligned memory access I think. Not sure whether all
architectures can handle it gracefully.

> > +	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@...il.com>");
> > +MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
> > +MODULE_LICENSE("GPL v2");
>

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