diff mbox series

[v5,2/2] iio: temperature: Add MCP9600 thermocouple EMF converter

Message ID 20230305213604.4747-3-andrew.hepp@ahepp.dev
State Superseded
Headers show
Series None | expand

Commit Message

Andrew Hepp March 5, 2023, 9:36 p.m. UTC 
Add support for the MCP9600 thermocouple EMF converter.

Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/MCP960X-Data-Sheet-20005426.pdf
Signed-off-by: Andrew Hepp <andrew.hepp@ahepp.dev>
---
Changes for v5:
- remove "driver" from subject
Changes for v4:
- none
Changes for v3:
- none
Changes for v2:
- remove unused sysfs include
- remove unused scan fields from channel
- warn rather than fail when probing unknown device
- register device through devm
- clean up style and prints
---
 drivers/iio/temperature/Kconfig   |  10 ++
 drivers/iio/temperature/Makefile  |   1 +
 drivers/iio/temperature/mcp9600.c | 146 ++++++++++++++++++++++++++++++
 3 files changed, 157 insertions(+)
 create mode 100644 drivers/iio/temperature/mcp9600.c

Comments

Jonathan Cameron March 12, 2023, 4:14 p.m. UTC | #1 
On Sun,  5 Mar 2023 13:36:04 -0800
Andrew Hepp <andrew.hepp@ahepp.dev> wrote:

> Add support for the MCP9600 thermocouple EMF converter.
> 
> Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/MCP960X-Data-Sheet-20005426.pdf
> Signed-off-by: Andrew Hepp <andrew.hepp@ahepp.dev>

Hi Andrew,

One minor improvement suggested inline.

If you can test with 
i2c_smbus_read_word_swapped() as suggested (I'm never sure when we need
the swapped form) that would be great.

If we had been later in the cycle I'd have taken this anyway and suggested
that change as a follow up patch, but we have lots of time, so no rush.

Thanks,

Jonathan

> +static int mcp9600_read(struct mcp9600_data *data,
> +			struct iio_chan_spec const *chan, int *val)
> +{
> +	__be16 buf;
> +	int ret;
> +
> +	mutex_lock(&data->read_lock);
> +	ret = i2c_smbus_read_i2c_block_data(data->client, chan->address, 2,
> +					    (u8 *)&buf);

Rare to see this call, so I went looking in the datasheet
https://www.kernel.org/doc/html/v5.5/i2c/smbus-protocol.html gives the structure
of this command as
S Addr Wr [A] Comm [A]
           S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P

which matches the datasheet. However for two bytes it's also the same as...

S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
which is the more common

i2c_smbus_read_word_data() which has a defined endian type and which
I think is the wrong one here.

Given that's a common situation we also have
i2c_smbus_read_word_swapped() which is same thing but for data the opposite
way around and will avoid the need for an explicit endian swap.

Jonathan



> +	mutex_unlock(&data->read_lock);
> +
> +	if (ret < 0)
> +		return ret;
> +	*val = be16_to_cpu(buf);
> +
> +	return 0;
> +}
> +
diff mbox series

Patch

diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
index ed384f33e0c7..ea2ce364b2e9 100644
--- a/drivers/iio/temperature/Kconfig
+++ b/drivers/iio/temperature/Kconfig
@@ -158,4 +158,14 @@  config MAX31865
 	  This driver can also be build as a module. If so, the module
 	  will be called max31865.
 
+config MCP9600
+	tristate "MCP9600 thermocouple EMF converter"
+	depends on I2C
+	help
+	  If you say yes here you get support for MCP9600
+	  thermocouple EMF converter connected via I2C.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called mcp9600.
+
 endmenu
diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile
index dfec8c6d3019..9330d4a39598 100644
--- a/drivers/iio/temperature/Makefile
+++ b/drivers/iio/temperature/Makefile
@@ -10,6 +10,7 @@  obj-$(CONFIG_MAXIM_THERMOCOUPLE) += maxim_thermocouple.o
 obj-$(CONFIG_MAX30208) += max30208.o
 obj-$(CONFIG_MAX31856) += max31856.o
 obj-$(CONFIG_MAX31865) += max31865.o
+obj-$(CONFIG_MCP9600) += mcp9600.o
 obj-$(CONFIG_MLX90614) += mlx90614.o
 obj-$(CONFIG_MLX90632) += mlx90632.o
 obj-$(CONFIG_TMP006) += tmp006.o
diff --git a/drivers/iio/temperature/mcp9600.c b/drivers/iio/temperature/mcp9600.c
new file mode 100644
index 000000000000..d938e09632cf
--- /dev/null
+++ b/drivers/iio/temperature/mcp9600.c
@@ -0,0 +1,146 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * mcp9600.c - Support for Microchip MCP9600 thermocouple EMF converter
+ *
+ * Copyright (c) 2022 Andrew Hepp
+ * Author: <andrew.hepp@ahepp.dev>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+
+/* MCP9600 registers */
+#define MCP9600_HOT_JUNCTION 0x0
+#define MCP9600_COLD_JUNCTION 0x2
+#define MCP9600_DEVICE_ID 0x20
+
+/* MCP9600 device id value */
+#define MCP9600_DEVICE_ID_MCP9600 0x40
+
+static const struct iio_chan_spec mcp9600_channels[] = {
+	{
+		.type = IIO_TEMP,
+		.address = MCP9600_HOT_JUNCTION,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+	},
+	{
+		.type = IIO_TEMP,
+		.address = MCP9600_COLD_JUNCTION,
+		.channel2 = IIO_MOD_TEMP_AMBIENT,
+		.modified = 1,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+struct mcp9600_data {
+	struct i2c_client *client;
+	struct mutex read_lock; /* lock to prevent concurrent reads */
+};
+
+static int mcp9600_read(struct mcp9600_data *data,
+			struct iio_chan_spec const *chan, int *val)
+{
+	__be16 buf;
+	int ret;
+
+	mutex_lock(&data->read_lock);
+	ret = i2c_smbus_read_i2c_block_data(data->client, chan->address, 2,
+					    (u8 *)&buf);
+	mutex_unlock(&data->read_lock);
+
+	if (ret < 0)
+		return ret;
+	*val = be16_to_cpu(buf);
+
+	return 0;
+}
+
+static int mcp9600_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct mcp9600_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = mcp9600_read(data, chan, val);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 62;
+		*val2 = 500000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info mcp9600_info = {
+	.read_raw = mcp9600_read_raw,
+};
+
+static int mcp9600_probe(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev;
+	struct mcp9600_data *data;
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(client, MCP9600_DEVICE_ID);
+	if (ret < 0)
+		return ret;
+	if (ret != MCP9600_DEVICE_ID_MCP9600)
+		dev_warn(&client->dev, "Expected ID %x, got %x\n",
+				MCP9600_DEVICE_ID_MCP9600, ret);
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+	mutex_init(&data->read_lock);
+
+	indio_dev->info = &mcp9600_info;
+	indio_dev->name = "mcp9600";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = mcp9600_channels;
+	indio_dev->num_channels = ARRAY_SIZE(mcp9600_channels);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id mcp9600_id[] = {
+	{ "mcp9600" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mcp9600_id);
+
+static const struct of_device_id mcp9600_of_match[] = {
+	{ .compatible = "microchip,mcp9600" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mcp9600_of_match);
+
+static struct i2c_driver mcp9600_driver = {
+	.driver = {
+		.name = "mcp9600",
+		.of_match_table = mcp9600_of_match,
+	},
+	.probe_new = mcp9600_probe,
+	.id_table = mcp9600_id
+};
+module_i2c_driver(mcp9600_driver);
+
+MODULE_AUTHOR("Andrew Hepp <andrew.hepp@ahepp.dev>");
+MODULE_DESCRIPTION("Microchip MCP9600 thermocouple EMF converter driver");
+MODULE_LICENSE("GPL");