[PATCH 2/2] hwmon: max31827: add MAX31827 driver

[Daniel Matyas <daniel.matyas@analog.com>]

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>
---
 MAINTAINERS              |   1 +
 drivers/hwmon/Kconfig    |  11 ++
 drivers/hwmon/Makefile   |   1 +
 drivers/hwmon/max31827.c | 240 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 253 insertions(+)
 create mode 100644 drivers/hwmon/max31827.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 549cea6bc340..63c17195a99b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12541,6 +12541,7 @@ L:	linux-hwmon@vger.kernel.org
 S:	Supported
 W:	http://ez.analog.com/community/linux-device-drivers
 F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
+F:	drivers/hwmon/max31827.c
 
 MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
 L:	linux-hwmon@vger.kernel.org
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 5b3b76477b0e..80c44a787d42 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -2401,4 +2401,15 @@ config SENSORS_ASUS_EC
 
 endif # ACPI
 
+config MAX31827
+	tristate "MAX31827 low-power temperature switch"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for MAX31827
+	  low-power temperature switch and sensor connected with I2C.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max31827.
+
 endif # HWMON
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 88712b5031c8..d00f0a1e73f6 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -224,3 +224,4 @@ obj-$(CONFIG_PMBUS)		+= pmbus/
 
 ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
 
+obj-$(CONFIG_MAX31827) += max31827.o
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
new file mode 100644
index 000000000000..1c79bcf12d78
--- /dev/null
+++ b/drivers/hwmon/max31827.c
@@ -0,0 +1,240 @@
+// 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/bits.h>
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.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_RESOL_MASK       GENMASK(7, 6)
+#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK BIT(14)
+#define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK BIT(15)
+
+#define MAX31827_CNV_SHUTDOWN			0x0
+#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_1SHOT_EN(x)			((x) ? BIT(0) : 0)
+
+struct max31827_state {
+	struct regmap *regmap;
+	struct i2c_client *client;
+};
+
+static const struct regmap_config max31827_regmap = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0xA,
+};
+
+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:
+			return 0444;
+		}
+	}
+
+	return 0;
+}
+
+static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long *val)
+{
+	struct max31827_state *st;
+	unsigned int uval;
+	int ret;
+
+	st = dev_get_drvdata(dev);
+	if (IS_ERR(st))
+		return PTR_ERR(st);
+
+	if (type != hwmon_temp)
+		return -EOPNOTSUPP;
+
+	switch (attr) {
+	case hwmon_temp_enable:
+		ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &uval);
+		uval  = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK, uval);
+		break;
+
+	case hwmon_temp_input:
+		ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
+		break;
+
+	case hwmon_temp_max:
+		ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
+		break;
+
+	case hwmon_temp_max_hyst:
+		ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG, &uval);
+		break;
+	case hwmon_temp_min:
+		ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
+		break;
+
+	case hwmon_temp_min_hyst:
+		ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG, &uval);
+		break;
+
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	if (ret)
+		return ret;
+
+	*val = uval;
+
+	return 0;
+}
+
+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);
+
+	if (IS_ERR(st))
+		return PTR_ERR(st);
+
+	switch (attr) {
+	case hwmon_temp_enable:
+		if (val >> 1)
+			return -EOPNOTSUPP;
+
+		return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+					  MAX31827_CONFIGURATION_1SHOT_MASK,
+					  MAX31827_1SHOT_EN(val));
+
+	case hwmon_temp_max:
+		return regmap_write(st->regmap, MAX31827_TH_REG, val);
+
+	case hwmon_temp_max_hyst:
+		return regmap_write(st->regmap, MAX31827_TH_HYST_REG, val);
+
+	case hwmon_temp_min:
+		return regmap_write(st->regmap, MAX31827_TL_REG, val);
+
+	case hwmon_temp_min_hyst:
+		return regmap_write(st->regmap, MAX31827_TL_HYST_REG, val);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int max31827_init_client(struct max31827_state *st)
+{
+	return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+				 MAX31827_CONFIGURATION_CNV_RATE_MASK |
+				 MAX31827_CONFIGURATION_1SHOT_MASK,
+				 MAX31827_1SHOT_EN(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_MAX | HWMON_T_MAX_HYST),
+	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 ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return -EOPNOTSUPP;
+
+	st = devm_kzalloc(dev, sizeof(struct max31827_state), GFP_KERNEL);
+	if (!st)
+		return -ENOMEM;
+
+	st->client = client;
+
+	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: %ld\n",
+				     PTR_ERR(st->regmap));
+
+	ret = max31827_init_client(st);
+	if (ret)
+		return ret;
+
+	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[] = {
+	{ .name = "max31827" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
+
+static const struct of_device_id max31827_of_match[] = {
+	{ .compatible = "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");
-- 
2.34.1