Date:   Sun, 5 Feb 2017 16:19:47 +0100 (CET)
From:   Peter Meerwald-Stadler <pmeerw@...erw.net>
To:     Tomasz Duszynski <tduszyns@...il.com>
cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        jic23@...nel.org, knaack.h@....de, lars@...afoo.de
Subject: Re: [PATCH 2/4] iio: chemical: add driver for dsm501/ppd42ns particle
 sensors


> This patch adds support for dsm501 and ppd42ns particle sensors.

quick comments below
 
> Both sensors work on the same principle. Heater (resistor) heats up air
> in sensor chamber which induces upward flow. Particles convect up through
> a light beam provided by internal infra-red LED. Light scattered by
> particles is picked by photodiode and internal electronics outputs PWM
> signal.
> 
> Measuring low time occupancy of the signal during 30s measurement period
> particles number in cubic meter can be computed.
> 
> Signed-off-by: Tomasz Duszynski <tduszyns@...il.com>
> ---
>  drivers/iio/chemical/Kconfig  |  10 ++
>  drivers/iio/chemical/Makefile |   1 +
>  drivers/iio/chemical/dsm501.c | 231 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 242 insertions(+)
>  create mode 100644 drivers/iio/chemical/dsm501.c
> 
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index cea7f9857a1f..986d612aa77f 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -21,6 +21,16 @@ config ATLAS_PH_SENSOR
>  	 To compile this driver as module, choose M here: the
>  	 module will be called atlas-ph-sensor.
>  
> +config DSM501
> +	tristate "Samyoung DSM501 particle sensor"
> +	depends on GPIOLIB
> +	help
> +	 Say yes here to build support for the Samyoung DSM501
> +	 particle sensor.
> +
> +	 To compile this driver as a module, choose M here: the module
> +	 will be called dsm501.
> +
>  config IAQCORE
>  	tristate "AMS iAQ-Core VOC sensors"
>  	depends on I2C
> diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> index b02202b41289..76f50ff8ba7d 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -4,5 +4,6 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_ATLAS_PH_SENSOR)	+= atlas-ph-sensor.o
> +obj-$(CONFIG_DSM501)		+= dsm501.o
>  obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
>  obj-$(CONFIG_VZ89X)		+= vz89x.o
> diff --git a/drivers/iio/chemical/dsm501.c b/drivers/iio/chemical/dsm501.c
> new file mode 100644
> index 000000000000..013f6b3bfd48
> --- /dev/null
> +++ b/drivers/iio/chemical/dsm501.c
> @@ -0,0 +1,231 @@
> +/*
> + * Samyoung DSM501 particle sensor driver
> + *
> + * Copyright (C) 2017 Tomasz Duszynski <tduszyns@...il.com>
> + *
> + * Datasheets:
> + *  http://www.samyoungsnc.com/products/3-1%20Specification%20DSM501.pdf
> + *  http://wiki.timelab.org/images/f/f9/PPD42NS.pdf
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/timekeeping.h>
> +
> +#define DSM501_DRV_NAME "dsm501"
> +#define	DSM501_IRQ_NAME "dsm501_irq"

replace tab by space

> +
> +#define DSM501_DEFAULT_MEASUREMENT_TIME 30 /* seconds */
> +
> +struct dsm501_data {
> +	ktime_t ts;
> +	ktime_t low_time;
> +	ktime_t meas_time;
> +
> +	int irq;
> +	struct gpio_desc *gpio;
> +
> +	struct mutex lock;
> +
> +	int (*number_concentration)(struct dsm501_data *data);
> +};
> +
> +/*
> + * Series of data points in Fig. 8-3 (Low Ratio vs Particle)
> + * can be approximated by following polynomials:
> + *
> + * p(r) = 0 (undefined) for r < 4
> + * p(r) = 2353564.2r - 4373814.7 for 4 <= r < 20
> + * p(r) = 4788112.4r - 53581390 for r >= 20
> + *
> + * Note: Result is in pcs/m3. To convert to pcs/0.01cf multiply
> + *	 by 0.0002831685.

is cf needed?

> + */
> +static int dsm501_number_concentartion(struct dsm501_data *data)
> +{
> +	s64 retval = 0, r = div64_s64(ktime_to_ns(data->low_time) * 100,
> +				      ktime_to_ns(data->meas_time));
> +
> +	if (r >= 4 && r < 20)
> +		retval = 23535642 * r - 43738147;
> +	else if (r >= 20)
> +		retval = 47881124 * r - 535813900;
> +
> +	return div_s64(retval, 10);
> +}
> +
> +/*
> + * Series of data points in Fig. 2 (Lo Pulse Occupancy Time vs Concentration)
> + * can be approximated by following polynomial:
> + *
> + * p(r) = 3844.2r^3 - 16201.3r^2 + 1848746.1r + 52497.2
> + *
> + * Note: Result is in pcs/m3. To convert to pcs/0.01cf multiply
> + *	 by 0.0002831685.
> + */
> +static int ppd42ns_number_concentration(struct dsm501_data *data)
> +{
> +	s64 retval, r3, r2, r = div64_s64(ktime_to_ns(data->low_time) * 100,
> +					  ktime_to_ns(data->meas_time));
> +
> +	r2 = r * r;
> +	r3 = r2 * r;
> +
> +	retval = 38442 * r3;
> +	retval -= 162013 * r2;
> +	retval += 18487461 * r;
> +	retval += 524972;
> +
> +	return div_s64(retval, 10);
> +}
> +
> +static irqreturn_t dsm501_irq(int irq, void *dev_id)
> +{
> +	struct dsm501_data *data = iio_priv(dev_id);
> +	int val = gpiod_get_value(data->gpio);
> +	ktime_t dt, ts = ktime_get();
> +
> +	if (ktime_to_ns(data->ts) == 0) {
> +		data->ts = ts;
> +		data->low_time = ktime_set(0, 0);
> +	}
> +
> +	if (val) {
> +		dt = ktime_sub(ts, data->ts);
> +		data->low_time = ktime_add(data->low_time, dt);
> +	} else {
> +		data->ts = ts;
> +	}

{} needed?

> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int dsm501_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int *val,
> +			   int *val2, long mask)
> +{
> +	struct dsm501_data *data = iio_priv(indio_dev);
> +	struct device *dev = indio_dev->dev.parent;
> +	unsigned long irqflags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;
> +	int ret;
> +
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		mutex_lock(&data->lock);
> +		data->ts = ktime_set(0, 0);
> +
> +		ret = devm_request_irq(dev, data->irq, dsm501_irq, irqflags,
> +				       DSM501_IRQ_NAME, indio_dev);

why devm_()? if the irq is explicitly freed below?
requesting the irq for every measurement seems weird even if it only 
happens every 30s

> +		if (ret) {
> +			dev_err(dev, "Failed to request interrupt %d\n", data->irq);
> +			mutex_unlock(&data->lock);
> +			return ret;
> +		}
> +
> +		msleep_interruptible(ktime_to_ms(data->meas_time));
> +		devm_free_irq(dev, data->irq, indio_dev);
> +
> +		*val = data->number_concentration(data);
> +		mutex_unlock(&data->lock);
> +
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info dsm501_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw = dsm501_read_raw,
> +};
> +
> +static const struct iio_chan_spec dsm501_channels[] = {
> +	{
> +		.type = IIO_NUMBERCONCENTRATION,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +	},
> +};
> +
> +static int dsm501_probe(struct platform_device *pdev)
> +{
> +	struct dsm501_data *data;
> +	struct iio_dev *indio_dev;
> +	struct device *dev = &pdev->dev;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	data->gpio = devm_gpiod_get_index(dev, NULL, 0, GPIOD_IN);
> +	if (IS_ERR(data->gpio)) {
> +		dev_err(dev, "Failed to get GPIO\n");
> +		return PTR_ERR(data->gpio);
> +	}
> +
> +	data->irq = gpiod_to_irq(data->gpio);
> +	if (data->irq < 0) {
> +		dev_err(dev, "GPIO has no interrupt\n");
> +		return data->irq;
> +	}
> +
> +	data->meas_time = ktime_set(DSM501_DEFAULT_MEASUREMENT_TIME, 0);
> +	data->number_concentration = of_device_get_match_data(dev);
> +	mutex_init(&data->lock);
> +
> +	indio_dev->name = DSM501_DRV_NAME;
> +	indio_dev->dev.parent = dev;
> +	indio_dev->info = &dsm501_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = dsm501_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(dsm501_channels);
> +
> +	return devm_iio_device_register(&pdev->dev, indio_dev);
> +}
> +
> +static const struct of_device_id dsm501_id[] = {
> +	{
> +		.compatible = "samyoung,dsm501",
> +		.data = dsm501_number_concentartion,

type: concentration

> +	},
> +	{
> +		.compatible = "shinyei,ppd42ns",
> +		.data = ppd42ns_number_concentration,
> +	},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, dsm501_id);
> +
> +static struct platform_driver dsm501_driver = {
> +	.driver	= {
> +		.name = DSM501_DRV_NAME,
> +		.of_match_table = of_match_ptr(dsm501_id)
> +	},
> +	.probe = dsm501_probe
> +};
> +module_platform_driver(dsm501_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tduszyns@...il.com>");
> +MODULE_DESCRIPTION("Samyoung DSM501 particle sensor driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)

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