Re: [PATCH v6] iio: temperature: add support for Maxim thermocouple chips

[Jonathan Cameron <jic23@kernel.org>]

On 10/07/16 14:26, Jonathan Cameron wrote:
> On 05/07/16 02:54, Matt Ranostay wrote:
>> Add initial driver support for MAX6675, and MAX31855 thermocouple chips.
>>
>> Cc: Marek Vasut <marex@denx.de>
>> Cc: Matt Porter <mporter@konsulko.com>
>> Signed-off-by: Matt Ranostay <mranostay@gmail.com>
> Hi Matt,
> 
> Very nice.  Applied to the togreg branch of iio.git.
> Initially pushed out as testing for the autobuilders to play with it.
> Unless Linus decides to delay the next merge window this has missed
> now I'm afraid.
> 
I forgot the small change to the get time function.  Fixed up.

Jonathan
> Jonathan
>> ---
>>
>> 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
>>
>> Changes from v3:
>> * fixed several typos of max31855 part number
>>
>> Changes from v4:
>> * drop maxim_thermocouple_validate_buffer() due to peer review saying
>>   this is an incorrect way to signal an invalid reading
>>
>> Changes from v5:
>>  * reorder struct maxim_thermocouple_chip to reduce alignment padding
>>  * add ____cacheline_aligned to the spi data buffer
>>
>> .../iio/temperature/maxim_thermocouple.txt         |  21 ++
>>  drivers/iio/temperature/Kconfig                    |  14 +
>>  drivers/iio/temperature/Makefile                   |   1 +
>>  drivers/iio/temperature/maxim_thermocouple.c       | 281 +++++++++++++++++++++
>>  4 files changed, 317 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 000000000000..28bc5c4d965b
>> --- /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,max31855" 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:
>> +
>> +	max31855@0 {
>> +		compatible = "maxim,max31855";
>> +		reg = <0>;
>> +		spi-max-frequency = <4300000>;
>> +	};
>> diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
>> index c4664e5de791..1d3da05eca39 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
>> +	   * MAX31855
>> +
>> +	  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 02bc79d49b24..78c3de0dc3f0 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 000000000000..62ae88bcc4e7
>> --- /dev/null
>> +++ b/drivers/iio/temperature/maxim_thermocouple.c
>> @@ -0,0 +1,281 @@
>> +/*
>> + * 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,
>> +	MAX31855,
>> +};
>> +
>> +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 max31855_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 max31855_scan_masks[] = {0x3, 0};
>> +
>> +struct maxim_thermocouple_chip {
>> +	const struct iio_chan_spec *channels;
>> +	const unsigned long *scan_masks;
>> +	u8 num_channels;
>> +	u8 read_size;
>> +
>> +	/* bit-check for valid input */
>> +	u32 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),
>> +		},
>> +	[MAX31855] = {
>> +			.channels = max31855_channels,
>> +			.num_channels = ARRAY_SIZE(max31855_channels),
>> +			.read_size = 4,
>> +			.scan_masks = max31855_scan_masks,
>> +			.status_bit = BIT(16),
>> +		},
>> +};
>> +
>> +struct maxim_thermocouple_data {
>> +	struct spi_device *spi;
>> +	const struct maxim_thermocouple_chip *chip;
>> +
>> +	u8 buffer[16] ____cacheline_aligned;
>> +};
>> +
>> +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 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) {
>> +		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:
>> +		ret = iio_device_claim_direct_mode(indio_dev);
>> +		if (ret)
>> +			return ret;
>> +
>> +		ret = maxim_thermocouple_read(data, chan, val);
>> +		iio_device_release_direct_mode(indio_dev);
>> +
>> +		if (!ret)
>> +			return IIO_VAL_INT;
>> +
>> +		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},
>> +	{"max31855", MAX31855},
>> +	{},
>> +};
>> +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");
>>
> 
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