hwmon: Add MAX31827 driver

MAX31827 is a low-power temperature switch with I2C interface.

The device is a ±1°C accuracy from -40°C to +125°C
(12 bits) local temperature switch and sensor with I2C/SM-
Bus interface. The combination of small 6-bump wafer-lev-
el package (WLP) and high accuracy makes this temper-
ature sensor/switch ideal for a wide range of applications.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
Link: https://lore.kernel.org/r/20230524160131.14081-2-daniel.matyas@analog.com
[groeck: Improved define alignment, return -EINVAL after bad user input,
 fixed up compatible statement]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 478 insertions, 1 deletions

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bf73934a6eee..c52e44a393e9 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1098,6 +1098,17 @@ config SENSORS_MAX31760
 	  This driver can also be built as a module. If so, the module
 	  will be called max31760.
 
+config MAX31827
+	tristate "MAX31827 low-power temperature switch and similar devices"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for MAX31827, MAX31828 and
+	  MAX31829 low-power temperature switches and sensors connected with I2C.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max31827.
+
 config SENSORS_MAX6620
 	tristate "Maxim MAX6620 fan controller"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index cd8c568c80a9..8a8021f9ca9e 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -149,6 +149,7 @@ obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o
 obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
 obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
 obj-$(CONFIG_SENSORS_MAX31790)	+= max31790.o
+obj-$(CONFIG_MAX31827) += max31827.o
 obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
 obj-$(CONFIG_SENSORS_MC34VR500)	+= mc34vr500.o
 obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
@@ -224,4 +225,3 @@ obj-$(CONFIG_SENSORS_PECI)	+= peci/
 obj-$(CONFIG_PMBUS)		+= pmbus/
 
 ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
-
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
new file mode 100644
index 000000000000..7735e8087df3
--- /dev/null
+++ b/drivers/hwmon/max31827.c
@@ -0,0 +1,466 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max31827.c - Support for Maxim Low-Power Switch
+ *
+ * Copyright (c) 2023 Daniel Matyas <daniel.matyas@analog.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+
+#define MAX31827_T_REG			0x0
+#define MAX31827_CONFIGURATION_REG	0x2
+#define MAX31827_TH_REG			0x4
+#define MAX31827_TL_REG			0x6
+#define MAX31827_TH_HYST_REG		0x8
+#define MAX31827_TL_HYST_REG		0xA
+
+#define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
+#define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
+#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK	BIT(14)
+#define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)
+
+#define MAX31827_12_BIT_CNV_TIME	141
+
+#define MAX31827_CNV_1_DIV_64_HZ	0x1
+#define MAX31827_CNV_1_DIV_32_HZ	0x2
+#define MAX31827_CNV_1_DIV_16_HZ	0x3
+#define MAX31827_CNV_1_DIV_4_HZ		0x4
+#define MAX31827_CNV_1_HZ		0x5
+#define MAX31827_CNV_4_HZ		0x6
+#define MAX31827_CNV_8_HZ		0x7
+
+#define MAX31827_16_BIT_TO_M_DGR(x)	(sign_extend32(x, 15) * 1000 / 16)
+#define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
+#define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
+
+struct max31827_state {
+	/*
+	 * Prevent simultaneous access to the i2c client.
+	 */
+	struct mutex lock;
+	struct regmap *regmap;
+	bool enable;
+};
+
+static const struct regmap_config max31827_regmap = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0xA,
+};
+
+static int write_alarm_val(struct max31827_state *st, unsigned int reg,
+			   long val)
+{
+	unsigned int cfg;
+	unsigned int tmp;
+	int ret;
+
+	val = MAX31827_M_DGR_TO_16_BIT(val);
+
+	/*
+	 * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold
+	 * register values are changed over I2C, the part must be in shutdown
+	 * mode.
+	 *
+	 * Mutex is used to ensure, that some other process doesn't change the
+	 * configuration register.
+	 */
+	mutex_lock(&st->lock);
+
+	if (!st->enable) {
+		ret = regmap_write(st->regmap, reg, val);
+		goto unlock;
+	}
+
+	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
+	if (ret)
+		goto unlock;
+
+	tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
+		      MAX31827_CONFIGURATION_CNV_RATE_MASK);
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(st->regmap, reg, val);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
+
+unlock:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static umode_t max31827_is_visible(const void *state,
+				   enum hwmon_sensor_types type, u32 attr,
+				   int channel)
+{
+	if (type == hwmon_temp) {
+		switch (attr) {
+		case hwmon_temp_enable:
+		case hwmon_temp_max:
+		case hwmon_temp_min:
+		case hwmon_temp_max_hyst:
+		case hwmon_temp_min_hyst:
+			return 0644;
+		case hwmon_temp_input:
+		case hwmon_temp_min_alarm:
+		case hwmon_temp_max_alarm:
+			return 0444;
+		default:
+			return 0;
+		}
+	} else if (type == hwmon_chip) {
+		if (attr == hwmon_chip_update_interval)
+			return 0644;
+	}
+
+	return 0;
+}
+
+static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long *val)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+	unsigned int uval;
+	int ret = 0;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_enable:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
+					 MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 uval);
+			*val = !!uval;
+
+			break;
+		case hwmon_temp_input:
+			mutex_lock(&st->lock);
+
+			if (!st->enable) {
+				/*
+				 * This operation requires mutex protection,
+				 * because the chip configuration should not
+				 * be changed during the conversion process.
+				 */
+
+				ret = regmap_update_bits(st->regmap,
+							 MAX31827_CONFIGURATION_REG,
+							 MAX31827_CONFIGURATION_1SHOT_MASK,
+							 1);
+				if (ret) {
+					mutex_unlock(&st->lock);
+					return ret;
+				}
+
+				msleep(MAX31827_12_BIT_CNV_TIME);
+			}
+			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
+
+			mutex_unlock(&st->lock);
+
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+
+			break;
+		case hwmon_temp_max:
+			ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_max_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
+					  &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_max_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
+					 uval);
+			break;
+		case hwmon_temp_min:
+			ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_min_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
+					  &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_min_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			*val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
+					 uval);
+			break;
+		default:
+			ret = -EOPNOTSUPP;
+			break;
+		}
+
+		break;
+
+	case hwmon_chip:
+		if (attr == hwmon_chip_update_interval) {
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 uval);
+			switch (uval) {
+			case MAX31827_CNV_1_DIV_64_HZ:
+				*val = 64000;
+				break;
+			case MAX31827_CNV_1_DIV_32_HZ:
+				*val = 32000;
+				break;
+			case MAX31827_CNV_1_DIV_16_HZ:
+				*val = 16000;
+				break;
+			case MAX31827_CNV_1_DIV_4_HZ:
+				*val = 4000;
+				break;
+			case MAX31827_CNV_1_HZ:
+				*val = 1000;
+				break;
+			case MAX31827_CNV_4_HZ:
+				*val = 250;
+				break;
+			case MAX31827_CNV_8_HZ:
+				*val = 125;
+				break;
+			default:
+				*val = 0;
+				break;
+			}
+		}
+		break;
+
+	default:
+		ret = -EOPNOTSUPP;
+		break;
+	}
+
+	return ret;
+}
+
+static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
+			  u32 attr, int channel, long val)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+	int ret;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_enable:
+			if (val >> 1)
+				return -EINVAL;
+
+			mutex_lock(&st->lock);
+			/**
+			 * The chip should not be enabled while a conversion is
+			 * performed. Neither should the chip be enabled when
+			 * the alarm values are changed.
+			 */
+
+			st->enable = val;
+
+			ret = regmap_update_bits(st->regmap,
+						 MAX31827_CONFIGURATION_REG,
+						 MAX31827_CONFIGURATION_1SHOT_MASK |
+						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						 MAX31827_DEVICE_ENABLE(val));
+
+			mutex_unlock(&st->lock);
+
+			return ret;
+
+		case hwmon_temp_max:
+			return write_alarm_val(st, MAX31827_TH_REG, val);
+
+		case hwmon_temp_max_hyst:
+			return write_alarm_val(st, MAX31827_TH_HYST_REG, val);
+
+		case hwmon_temp_min:
+			return write_alarm_val(st, MAX31827_TL_REG, val);
+
+		case hwmon_temp_min_hyst:
+			return write_alarm_val(st, MAX31827_TL_HYST_REG, val);
+
+		default:
+			return -EOPNOTSUPP;
+		}
+
+	case hwmon_chip:
+		if (attr == hwmon_chip_update_interval) {
+			if (!st->enable)
+				return -EINVAL;
+
+			switch (val) {
+			case 125:
+				val = MAX31827_CNV_8_HZ;
+				break;
+			case 250:
+				val = MAX31827_CNV_4_HZ;
+				break;
+			case 1000:
+				val = MAX31827_CNV_1_HZ;
+				break;
+			case 4000:
+				val = MAX31827_CNV_1_DIV_4_HZ;
+				break;
+			case 16000:
+				val = MAX31827_CNV_1_DIV_16_HZ;
+				break;
+			case 32000:
+				val = MAX31827_CNV_1_DIV_32_HZ;
+				break;
+			case 64000:
+				val = MAX31827_CNV_1_DIV_64_HZ;
+				break;
+			default:
+				return -EINVAL;
+			}
+
+			val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 val);
+
+			return regmap_update_bits(st->regmap,
+						  MAX31827_CONFIGURATION_REG,
+						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						  val);
+		}
+		break;
+
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int max31827_init_client(struct max31827_state *st)
+{
+	st->enable = true;
+
+	return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+				  MAX31827_CONFIGURATION_1SHOT_MASK |
+					  MAX31827_CONFIGURATION_CNV_RATE_MASK,
+				  MAX31827_DEVICE_ENABLE(1));
+}
+
+static const struct hwmon_channel_info *max31827_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
+					 HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM |
+					 HWMON_T_MAX | HWMON_T_MAX_HYST |
+					 HWMON_T_MAX_ALARM),
+	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
+	NULL,
+};
+
+static const struct hwmon_ops max31827_hwmon_ops = {
+	.is_visible = max31827_is_visible,
+	.read = max31827_read,
+	.write = max31827_write,
+};
+
+static const struct hwmon_chip_info max31827_chip_info = {
+	.ops = &max31827_hwmon_ops,
+	.info = max31827_info,
+};
+
+static int max31827_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct max31827_state *st;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return -EOPNOTSUPP;
+
+	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return -ENOMEM;
+
+	mutex_init(&st->lock);
+
+	st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap),
+				     "Failed to allocate regmap.\n");
+
+	err = max31827_init_client(st);
+	if (err)
+		return err;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
+							 &max31827_chip_info,
+							 NULL);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max31827_i2c_ids[] = {
+	{ "max31827", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
+
+static const struct of_device_id max31827_of_match[] = {
+	{ .compatible = "adi,max31827" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max31827_of_match);
+
+static struct i2c_driver max31827_driver = {
+	.class = I2C_CLASS_HWMON,
+	.driver = {
+		.name = "max31827",
+		.of_match_table = max31827_of_match,
+	},
+	.probe_new = max31827_probe,
+	.id_table = max31827_i2c_ids,
+};
+module_i2c_driver(max31827_driver);
+
+MODULE_AUTHOR("Daniel Matyas <daniel.matyas@analog.com>");
+MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
+MODULE_LICENSE("GPL");