[lm-sensors] [PATCH 1/2] hwmon: (max31722) Add support for MAX31722/MAX31723 temperature sensors

[Tiberiu Breana <tiberiu.a.breana@intel.com>]

Add basic support for the Maxim Integrated MAX31722/MAX31723 SPI
temperature sensors / thermostats.

Includes:
    - ACPI support;
    - raw temperature readings;
    - power management

Datasheet:
https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf

Signed-off-by: Tiberiu Breana <tiberiu.a.breana@intel.com>
---
 Documentation/hwmon/max31722 |  34 +++++
 drivers/hwmon/Kconfig        |  11 ++
 drivers/hwmon/Makefile       |   1 +
 drivers/hwmon/max31722.c     | 304 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 350 insertions(+)
 create mode 100644 Documentation/hwmon/max31722
 create mode 100644 drivers/hwmon/max31722.c

diff --git a/Documentation/hwmon/max31722 b/Documentation/hwmon/max31722
new file mode 100644
index 0000000..090da845
--- /dev/null
+++ b/Documentation/hwmon/max31722
@@ -0,0 +1,34 @@
+Kernel driver max31722
+===========
+
+Supported chips:
+  * Maxim Integrated MAX31722
+    Prefix: 'max31722'
+    ACPI ID: MAX31722
+    Addresses scanned: -
+    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+  * Maxim Integrated MAX31723
+    Prefix: 'max31723'
+    ACPI ID: MAX31723
+    Addresses scanned: -
+    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+
+Author: Tiberiu Breana <tiberiu.a.breana@intel.com>
+
+Description
+-----------
+
+This driver adds support for the Maxim Integrated MAX31722/MAX31723 thermometers
+and thermostats running over an SPI interface.
+
+Usage Notes
+-----------
+
+This driver uses ACPI to auto-detect devices. See ACPI IDs in the above section.
+
+Sysfs entries
+-------------
+
+The following attribute is supported:
+
+temp1_input		Measured temperature. Read-only.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 5c2d13a..714be75 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -821,6 +821,17 @@ config SENSORS_MAX197
 	  This driver can also be built as a module. If so, the module
 	  will be called max197.
 
+config SENSORS_MAX31722
+tristate "MAX31722 temperature sensor"
+	depends on SPI
+	select REGMAP_SPI
+	help
+	  Support for the Maxim Integrated MAX31722/MAX31723 digital
+	  thermometers/thermostats operating over an SPI interface.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called max31722.
+
 config SENSORS_MAX6639
 	tristate "Maxim MAX6639 sensor chip"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 58cc3ac..2ef5b7c 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -112,6 +112,7 @@ obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
 obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
 obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
 obj-$(CONFIG_SENSORS_MAX197)	+= max197.o
+obj-$(CONFIG_SENSORS_MAX31722)	+= max31722.o
 obj-$(CONFIG_SENSORS_MAX6639)	+= max6639.o
 obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o
 obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
diff --git a/drivers/hwmon/max31722.c b/drivers/hwmon/max31722.c
new file mode 100644
index 0000000..13ba906
--- /dev/null
+++ b/drivers/hwmon/max31722.c
@@ -0,0 +1,304 @@
+/*
+ * max31722 - hwmon driver for Maxim Integrated MAX31722/MAX31723 SPI
+ * digital thermometer and thermostats.
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License. See the file COPYING in the main
+ * directory of this archive for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+
+#define MAX31722_REG_CFG				0x00
+#define MAX31722_REG_TEMP_LSB				0x01
+#define MAX31722_REG_TEMP_MSB				0x02
+#define MAX31722_MAX_REG				0x86
+
+#define MAX31722_MODE_CONTINUOUS			0x00
+#define MAX31722_MODE_STANDBY				0x01
+#define MAX31722_RESOLUTION_11BIT			0x02
+
+#define MAX31722_REGMAP_NAME				"max31722_regmap"
+
+#define MAX31722_REGFIELD(name)						    \
+	do {								    \
+		data->reg_##name =					    \
+			devm_regmap_field_alloc(&spi->dev, regmap,	    \
+				max31722_reg_field_##name);		    \
+		if (IS_ERR(data->reg_##name)) {				    \
+			dev_err(&spi->dev, "reg field alloc failed.\n");    \
+			return PTR_ERR(data->reg_##name);		    \
+		}							    \
+	} while (0)
+
+struct max31722_data {
+	struct spi_device *spi_device;
+	struct device *hwmon_dev;
+	struct regmap *regmap;
+	struct regmap_field *reg_state;
+	struct regmap_field *reg_resolution;
+};
+
+/*
+ * This is a negative exponent value lookup table (as millidegree units)
+ * for calculating LSB values. The value corresponding to the fourth LSB
+ * bit is missing, as it is not used.
+ */
+static const int max31722_milli_table[3] = {
+	500, 250, 125
+};
+
+static const struct reg_field max31722_reg_field_state +				REG_FIELD(MAX31722_REG_CFG, 0, 0);
+static const struct reg_field max31722_reg_field_resolution +				REG_FIELD(MAX31722_REG_CFG, 1, 2);
+
+static bool max31722_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MAX31722_REG_TEMP_LSB:
+	case MAX31722_REG_TEMP_MSB:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool max31722_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MAX31722_REG_TEMP_LSB:
+	case MAX31722_REG_TEMP_MSB:
+		return false;
+	default:
+		return true;
+	}
+}
+
+static struct regmap_config max31722_regmap_config = {
+	.name = MAX31722_REGMAP_NAME,
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = MAX31722_MAX_REG,
+	.cache_type = REGCACHE_RBTREE,
+
+	.volatile_reg = max31722_is_volatile_reg,
+	.writeable_reg = max31722_is_writeable_reg,
+
+	.read_flag_mask = 0x00,
+	.write_flag_mask = 0x80,
+};
+
+static int max31722_set_mode(struct max31722_data *data, u8 mode)
+{
+	int ret;
+	struct spi_device *spi = data->spi_device;
+
+	ret = regmap_field_write(data->reg_state, mode);
+	if (ret < 0)
+		dev_err(&spi->dev, "failed to set sensor mode.\n");
+
+	return ret;
+}
+
+static ssize_t max31722_show_name(struct device *dev,
+				  struct device_attribute *devattr,
+				  char *buf)
+{
+	return sprintf(buf, "%s\n", to_spi_device(dev)->modalias);
+}
+
+static ssize_t max31722_show_temperature(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	int i;
+	int ret;
+	u8 lsb;
+	s16 val;
+	u16 temp;
+	struct max31722_data *data = dev_get_drvdata(dev);
+
+	ret = regmap_bulk_read(data->regmap, MAX31722_REG_TEMP_LSB, &temp, 2);
+	if (ret < 0) {
+		dev_err(&data->spi_device->dev,
+			"failed to read temperature register\n");
+		return ret;
+	}
+	/*
+	 * The MSB contains the integer part of the temperature value
+	 * (signed), while the LSB contains the fractional part as
+	 * negative powers of 2, e.g.: bit 0 is 2^-1, bit 1 is 2^-2, etc.
+	 * Temperature is exported in millidegrees Celsius.
+	 */
+	val = (temp >> 8) * 1000;
+	lsb = (temp << 8) >> 13; /* We only need the first 3 LSB bits. */
+	i = 0;
+	while (i < 3) {
+		if ((lsb >> (3 - i - 1)) & 0x01)
+			val += max31722_milli_table[i];
+		i++;
+	}
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static DEVICE_ATTR(name, S_IRUGO, max31722_show_name, NULL);
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
+			  max31722_show_temperature, NULL, 0);
+
+static struct attribute *max31722_attributes[] = {
+	&dev_attr_name.attr,
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group max31722_group = {
+	.attrs = max31722_attributes,
+};
+
+static int max31722_init(struct max31722_data *data)
+{
+	int ret = 0;
+	struct spi_device *spi = data->spi_device;
+	struct regmap *regmap;
+
+	/* Initialize the regmap */
+	regmap = devm_regmap_init_spi(spi, &max31722_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&spi->dev, "regmap initialization failed.\n");
+		return PTR_ERR(regmap);
+	}
+	data->regmap = regmap;
+
+	MAX31722_REGFIELD(state);
+	MAX31722_REGFIELD(resolution);
+
+	/* Set SD bit to 0 so we can have continuous measurements. */
+	ret = regmap_field_write(data->reg_state, MAX31722_MODE_CONTINUOUS);
+	if (ret < 0)
+		goto err;
+	/*
+	 * Set resolution to 11 bits (3 decimals) so we can have the maximum
+	 * precision in the exported millidegree range.
+	 */
+	ret = regmap_field_write(data->reg_resolution,
+				 MAX31722_RESOLUTION_11BIT);
+	if (ret < 0)
+		goto err;
+
+	return 0;
+
+err:
+	dev_err(&spi->dev, "sensor configuration failed.\n");
+	return ret;
+}
+
+static int max31722_probe(struct spi_device *spi)
+{
+	int ret;
+	struct max31722_data *data;
+
+	data = devm_kzalloc(&spi->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	spi_set_drvdata(spi, data);
+	data->spi_device = spi;
+
+	ret = max31722_init(data);
+	if (ret < 0)
+		goto err_standby;
+
+	ret = sysfs_create_group(&spi->dev.kobj, &max31722_group);
+	if (ret < 0)
+		goto err_standby;
+
+	data->hwmon_dev = hwmon_device_register(&spi->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		ret = PTR_ERR(data->hwmon_dev);
+		goto err_remove_group;
+	}
+
+	return 0;
+
+err_remove_group:
+	sysfs_remove_group(&spi->dev.kobj, &max31722_group);
+err_standby:
+	max31722_set_mode(data, MAX31722_MODE_STANDBY);
+	return ret;
+}
+
+static int max31722_remove(struct spi_device *spi)
+{
+	struct max31722_data *data = spi_get_drvdata(spi);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&spi->dev.kobj, &max31722_group);
+
+	return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int max31722_suspend(struct device *dev)
+{
+	struct spi_device *spi_device = to_spi_device(dev);
+	struct max31722_data *data = spi_get_drvdata(spi_device);
+
+	return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+static int max31722_resume(struct device *dev)
+{
+	struct spi_device *spi_device = to_spi_device(dev);
+	struct max31722_data *data = spi_get_drvdata(spi_device);
+
+	return max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
+}
+
+static SIMPLE_DEV_PM_OPS(max31722_pm_ops, max31722_suspend, max31722_resume);
+
+#define MAX31722_PM_OPS (&max31722_pm_ops)
+#else
+#define MAX31722_PM_OPS NULL
+#endif
+
+static const struct spi_device_id max31722_spi_id[] = {
+	{"max31722", 0},
+	{"max31723", 0},
+	{}
+};
+
+static const struct acpi_device_id max31722_acpi_id[] = {
+	{"MAX31722", 0},
+	{"MAX31723", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(spi, max31722_spi_id);
+
+static struct spi_driver max31722_driver = {
+	.driver = {
+		.name = "max31722",
+		.pm = MAX31722_PM_OPS,
+		.acpi_match_table = ACPI_PTR(max31722_acpi_id),
+	},
+	.probe =            max31722_probe,
+	.remove =           max31722_remove,
+	.id_table =         max31722_spi_id,
+};
+
+module_spi_driver(max31722_driver);
+
+MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
+MODULE_DESCRIPTION("max31722 sensor driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1


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