Re: [PATCH v3] iio: temperature: add support for Maxim thermocouple chips

[Jonathan Cameron <jic23@kernel.org>]

On 30/05/16 02:37, Matt Ranostay wrote:
> Add initial driver support for MAX6675, and MAX31885 thermocouple chips.
> 
> Cc: Marek Vasut <marex@denx.de>
> Cc: Matt Porter <mporter@konsulko.com>
> Signed-off-by: Matt Ranostay <mranostay@gmail.com>
I'm going to let this sit for a sort while as I'd like some discussion
of the invalidate buffer bit.

Cc'd a few more people for views.

> ---
> 
> Changes from v1:
> * switch to iio_device_*_direct_mode wrappers
> * add const to structs
> * removed useless cast
> 
> Changes from v2:
> * mark buffer data invalid on disconnected thermocouple
> * add .address = 0 to be consistent
> * add missing scan_mask for the max31855 part
> 
> .../iio/temperature/maxim_thermocouple.txt         |  21 ++
>  drivers/iio/temperature/Kconfig                    |  14 +
>  drivers/iio/temperature/Makefile                   |   1 +
>  drivers/iio/temperature/maxim_thermocouple.c       | 300 +++++++++++++++++++++
>  4 files changed, 336 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt
>  create mode 100644 drivers/iio/temperature/maxim_thermocouple.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt b/Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt
> new file mode 100644
> index 0000000..44fb029
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt
> @@ -0,0 +1,21 @@
> +Maxim thermocouple support
> +
> +* https://datasheets.maximintegrated.com/en/ds/MAX6675.pdf
> +* https://datasheets.maximintegrated.com/en/ds/MAX31855.pdf
> +
> +Required properties:
> +
> +	- compatible: must be "maxim,max31885" or "maxim,max6675"
> +	- reg: SPI chip select number for the device
> +	- spi-max-frequency: must be 4300000
> +	- spi-cpha: must be defined for max6675 to enable SPI mode 1
> +
> +	Refer to spi/spi-bus.txt for generic SPI slave bindings.
> +
> +Example:
> +
> +	max31885@0 {
> +		compatible = "maxim,max31885";
> +		reg = <0>;
> +		spi-max-frequency = <4300000>;
> +	};
> diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
> index c4664e5..c9f5342 100644
> --- a/drivers/iio/temperature/Kconfig
> +++ b/drivers/iio/temperature/Kconfig
> @@ -3,6 +3,20 @@
>  #
>  menu "Temperature sensors"
>  
> +config MAXIM_THERMOCOUPLE
> +	tristate "Maxim thermocouple sensors"
> +	depends on SPI
> +	help
> +	  If you say yes here you get support for the Maxim series of
> +	  thermocouple sensors connected via SPI.
> +
> +	  Supported sensors:
> +	   * MAX6675
> +	   * MAX31885
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called maxim_thermocouple.
> +
>  config MLX90614
>  	tristate "MLX90614 contact-less infrared sensor"
>  	depends on I2C
> diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile
> index 02bc79d..78c3de0 100644
> --- a/drivers/iio/temperature/Makefile
> +++ b/drivers/iio/temperature/Makefile
> @@ -2,6 +2,7 @@
>  # Makefile for industrial I/O temperature drivers
>  #
>  
> +obj-$(CONFIG_MAXIM_THERMOCOUPLE) += maxim_thermocouple.o
>  obj-$(CONFIG_MLX90614) += mlx90614.o
>  obj-$(CONFIG_TMP006) += tmp006.o
>  obj-$(CONFIG_TSYS01) += tsys01.o
> diff --git a/drivers/iio/temperature/maxim_thermocouple.c b/drivers/iio/temperature/maxim_thermocouple.c
> new file mode 100644
> index 0000000..59ef7fd
> --- /dev/null
> +++ b/drivers/iio/temperature/maxim_thermocouple.c
> @@ -0,0 +1,300 @@
> +/*
> + * maxim_thermocouple.c  - Support for Maxim thermocouple chips
> + *
> + * Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
> + *
> + * 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/module.h>
> +#include <linux/init.h>
> +#include <linux/mutex.h>
> +#include <linux/err.h>
> +#include <linux/spi/spi.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +
> +#define MAXIM_THERMOCOUPLE_DRV_NAME	"maxim_thermocouple"
> +
> +enum {
> +	MAX6675,
> +	MAX31885,
> +};
> +
> +const struct iio_chan_spec max6675_channels[] = {
> +	{	/* thermocouple temperature */
> +		.type = IIO_TEMP,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 13,
> +			.storagebits = 16,
> +			.shift = 3,
> +			.endianness = IIO_BE,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(1),
> +};
> +
> +const struct iio_chan_spec max31885_channels[] = {
> +	{	/* thermocouple temperature */
> +		.type = IIO_TEMP,
> +		.address = 2,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 14,
> +			.storagebits = 16,
> +			.shift = 2,
> +			.endianness = IIO_BE,
> +		},
> +	},
> +	{	/* cold junction temperature */
> +		.type = IIO_TEMP,
> +		.address = 0,
> +		.channel2 = IIO_MOD_TEMP_AMBIENT,
> +		.modified = 1,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 1,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 4,
> +			.endianness = IIO_BE,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(2),
> +};
> +
> +static const unsigned long max31885_scan_masks[] = {0x3, 0};
> +
> +struct maxim_thermocouple_chip {
> +	const struct iio_chan_spec *channels;
> +	const unsigned long *scan_masks;
> +	int num_channels;
> +	int read_size;
> +
> +	/* bit-check for valid input */
> +	int status_bit;
> +};
> +
> +const struct maxim_thermocouple_chip maxim_thermocouple_chips[] = {
> +	[MAX6675] = {
> +			.channels = max6675_channels,
> +			.num_channels = ARRAY_SIZE(max6675_channels),
> +			.read_size = 2,
> +			.status_bit = BIT(2),
> +		},
> +	[MAX31885] = {
> +			.channels = max31885_channels,
> +			.num_channels = ARRAY_SIZE(max31885_channels),
> +			.read_size = 4,
> +			.scan_masks = max31885_scan_masks,
> +			.status_bit = BIT(16),
> +		},
> +};
> +
> +struct maxim_thermocouple_data {
> +	struct spi_device *spi;
> +	const struct maxim_thermocouple_chip *chip;
> +
> +	u8 buffer[16]; /* 4 byte data + 4 byte padding + 8 byte timestamp */
> +};
> +
> +static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
> +				   struct iio_chan_spec const *chan, int *val)
> +{
> +	unsigned int storage_bytes = data->chip->read_size;
> +	unsigned int shift = chan->scan_type.shift + (chan->address * 8);
> +	unsigned int buf;
> +	int ret;
> +
> +	ret = spi_read(data->spi, (void *) &buf, storage_bytes);
> +	if (ret)
> +		return ret;
> +
> +	switch (storage_bytes) {
> +	case 2:
> +		*val = be16_to_cpu(buf);
> +		break;
> +	case 4:
> +		*val = be32_to_cpu(buf);
> +		break;
> +	}
> +
> +	/* check to be sure this is a valid reading */
> +	if (*val & data->chip->status_bit)
> +		return -EINVAL;
> +
> +	*val = sign_extend32(*val >> shift, chan->scan_type.realbits - 1);
> +
> +	return 0;
> +}
> +
> +static void maxim_thermocouple_validate_buffer(struct maxim_thermocouple_data *data)
> +{
> +	unsigned int storage_bytes = data->chip->read_size;
> +	unsigned int *buf = (unsigned int *) data->buffer;
> +	int tmp = 0;
> +
> +	switch (storage_bytes) {
> +	case 2:
> +		tmp = be16_to_cpu(*buf);
> +		break;
> +	case 4:
> +		tmp = be32_to_cpu(*buf);
> +		break;
> +	}
> +
> +	/* check to be sure this is a valid reading, mark result -1 if not */
> +	if (tmp & data->chip->status_bit)
> +		memset(data->buffer, 0xff, storage_bytes);
> +}
> +
> +static irqreturn_t maxim_thermocouple_trigger_handler(int irq, void *private)
> +{
> +	struct iio_poll_func *pf = private;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct maxim_thermocouple_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = spi_read(data->spi, data->buffer, data->chip->read_size);
> +	if (!ret) {
> +		maxim_thermocouple_validate_buffer(data);
> +		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> +						   iio_get_time_ns());
> +	}
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int maxim_thermocouple_read_raw(struct iio_dev *indio_dev,
> +				       struct iio_chan_spec const *chan,
> +				       int *val, int *val2, long mask)
> +{
> +	struct maxim_thermocouple_data *data = iio_priv(indio_dev);
> +	int ret = -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (iio_device_claim_direct_mode(indio_dev))
> +			return -EBUSY;
> +
> +		ret = maxim_thermocouple_read(data, chan, val);
> +		if (!ret)
> +			ret = IIO_VAL_INT;
> +
> +		iio_device_release_direct_mode(indio_dev);
> +		break;
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->channel2) {
> +		case IIO_MOD_TEMP_AMBIENT:
> +			*val = 62;
> +			*val2 = 500000; /* 1000 * 0.0625 */
> +			ret = IIO_VAL_INT_PLUS_MICRO;
> +			break;
> +		default:
> +			*val = 250; /* 1000 * 0.25 */
> +			ret = IIO_VAL_INT;
> +		};
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct iio_info maxim_thermocouple_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = maxim_thermocouple_read_raw,
> +};
> +
> +static int maxim_thermocouple_probe(struct spi_device *spi)
> +{
> +	const struct spi_device_id *id = spi_get_device_id(spi);
> +	struct iio_dev *indio_dev;
> +	struct maxim_thermocouple_data *data;
> +	const struct maxim_thermocouple_chip *chip =
> +			&maxim_thermocouple_chips[id->driver_data];
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	indio_dev->info = &maxim_thermocouple_info;
> +	indio_dev->name = MAXIM_THERMOCOUPLE_DRV_NAME;
> +	indio_dev->channels = chip->channels;
> +	indio_dev->available_scan_masks = chip->scan_masks;
> +	indio_dev->num_channels = chip->num_channels;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	data = iio_priv(indio_dev);
> +	data->spi = spi;
> +	data->chip = chip;
> +
> +	ret = iio_triggered_buffer_setup(indio_dev, NULL,
> +				maxim_thermocouple_trigger_handler, NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto error_unreg_buffer;
> +
> +	return 0;
> +
> +error_unreg_buffer:
> +	iio_triggered_buffer_cleanup(indio_dev);
> +
> +	return ret;
> +}
> +
> +static int maxim_thermocouple_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +
> +	iio_device_unregister(indio_dev);
> +	iio_triggered_buffer_cleanup(indio_dev);
> +
> +	return 0;
> +}
> +
> +static const struct spi_device_id maxim_thermocouple_id[] = {
> +	{"max6675", MAX6675},
> +	{"max31885", MAX31885},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(spi, maxim_thermocouple_id);
> +
> +static struct spi_driver maxim_thermocouple_driver = {
> +	.driver = {
> +		.name	= MAXIM_THERMOCOUPLE_DRV_NAME,
> +	},
> +	.probe		= maxim_thermocouple_probe,
> +	.remove		= maxim_thermocouple_remove,
> +	.id_table	= maxim_thermocouple_id,
> +};
> +module_spi_driver(maxim_thermocouple_driver);
> +
> +MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
> +MODULE_DESCRIPTION("Maxim thermocouple sensors");
> +MODULE_LICENSE("GPL");
>