hwmon: (pmbus/lt3074) add support for lt3074

Add hardware monitoring and regulator support for LT3074. The LT3074 is an
ultrafast, ultralow noise 3A, 5.5V dropout linear regulator. The PMBus
serial interface allows telemetry for input/output voltage, bias voltage,
output current, and die temperature.

Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
Link: https://lore.kernel.org/r/20250421-upstream-lt3074-v3-2-71636322f9fe@analog.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/index.rst

@@ -126,6 +126,7 @@ Hardware Monitoring Kernel Drivers
    lm95234
    lm95245
    lochnagar
+   lt3074
    lt7182s
    ltc2992
    ltc2945

Documentation/hwmon/lt3074.rst

@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver lt3074
+====================
+
+Supported chips:
+
+  * Analog Devices LT3074
+
+    Prefix: 'lt3074'
+
+    Addresses scanned: -
+
+    Datasheet: https://www.analog.com/en/products/lt3074.html
+
+Authors: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
+
+
+Description
+-----------
+
+This driver supports hardware monitoring for Analog Devices LT3074 Linear
+Regulator with PMBus interface.
+
+The LT3074 is a low voltage, ultra-low noise and ultra-fast transient
+response linear regulator with PMBus serial interface. PMBus telemetry
+feature provides information regarding the output voltage and current,
+input voltage, bias voltage and die temperature.
+
+The driver is a client driver to the core PMBus driver. Please see
+Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate
+the devices explicitly. Please see Documentation/i2c/instantiating-devices.rst
+for details.
+
+Platform data support
+---------------------
+
+The driver supports standard PMBus driver platform data.
+
+Sysfs entries
+-------------
+
+======================= =======================================================
+in1_label		"vin"
+in1_input		Measured input voltage
+in1_max			Input overvoltage warning limit
+in1_max_alarm		Input overvoltage warning status
+in1_min			Input undervoltage warning limit
+in1_min_alarm		Input undervoltage warning status
+in2_label		"vmon"
+in2_input		Measured bias voltage
+in2_max			Bias overvoltage warning limit
+in2_min			Bias undervoltage warning limit
+in3_label		"vout1"
+in3_input		Measured output voltage
+in3_max			Output overvoltage warning limit
+in3_max_alarm		Output overvoltage warning status
+in3_min			Output undervoltage warning limit
+in3_min_alarm		Output undervoltage warning status
+curr1_label		"iout1"
+curr1_input		Measured output current.
+curr1_crit		Output overcurrent fault limit
+curr1_crit_alarm	Output overcurrent fault status
+temp1_input		Measured temperature
+temp1_max		Maximum temperature limit
+temp1_max_alarm		Overtemperature warning status
+======================= =======================================================

MAINTAINERS

@@ -13995,6 +13995,8 @@ L:	linux-hwmon@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/hwmon/pmbus/adi,lt3074.yaml
+F:	Documentation/hwmon/lt3074.rst
+F:	drivers/hwmon/pmbus/lt3074.c
 
 LTC1660 DAC DRIVER
 M:	Marcus Folkesson <marcus.folkesson@gmail.com>

drivers/hwmon/pmbus/Kconfig

@@ -218,6 +218,24 @@ config SENSORS_LM25066_REGULATOR
 	  If you say yes here you get regulator support for National
 	  Semiconductor LM25066, LM5064, and LM5066.
 
+config SENSORS_LT3074
+	tristate "Analog Devices LT3074"
+	help
+	  If you say yes here you get hardware monitoring support for Analog
+	  Devices LT3074.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called lt3074.
+
+config SENSORS_LT3074_REGULATOR
+	tristate "Regulator support for LT3074"
+	depends on SENSORS_LT3074 && REGULATOR
+	help
+	  If you say yes here you get regulator support for Analog Devices
+	  LT3074. The LT3074 is a low voltage, ultralow noise, high PSRR,
+	  dropout linear regulator. The device supplies up to 3A with a
+	  typical dropout voltage of 45mV.
+
 config SENSORS_LT7182S
 	tristate "Analog Devices LT7182S"
 	help

drivers/hwmon/pmbus/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_SENSORS_IR38064)	+= ir38064.o
 obj-$(CONFIG_SENSORS_IRPS5401)	+= irps5401.o
 obj-$(CONFIG_SENSORS_ISL68137)	+= isl68137.o
 obj-$(CONFIG_SENSORS_LM25066)	+= lm25066.o
+obj-$(CONFIG_SENSORS_LT3074)	+= lt3074.o
 obj-$(CONFIG_SENSORS_LT7182S)	+= lt7182s.o
 obj-$(CONFIG_SENSORS_LTC2978)	+= ltc2978.o
 obj-$(CONFIG_SENSORS_LTC3815)	+= ltc3815.o

drivers/hwmon/pmbus/lt3074.c

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hardware monitoring driver for Analog Devices LT3074
+ *
+ * Copyright (C) 2025 Analog Devices, Inc.
+ */
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+
+#include "pmbus.h"
+
+#define LT3074_MFR_READ_VBIAS			0xc6
+#define LT3074_MFR_BIAS_OV_WARN_LIMIT		0xc7
+#define LT3074_MFR_BIAS_UV_WARN_LIMIT		0xc8
+#define LT3074_MFR_SPECIAL_ID			0xe7
+
+#define LT3074_SPECIAL_ID_VALUE			0x1c1d
+
+static const struct regulator_desc __maybe_unused lt3074_reg_desc[] = {
+	PMBUS_REGULATOR_ONE("regulator"),
+};
+
+static int lt3074_read_word_data(struct i2c_client *client, int page,
+				 int phase, int reg)
+{
+	switch (reg) {
+	case PMBUS_VIRT_READ_VMON:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_READ_VBIAS);
+	case PMBUS_VIRT_VMON_UV_WARN_LIMIT:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_BIAS_UV_WARN_LIMIT);
+	case PMBUS_VIRT_VMON_OV_WARN_LIMIT:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_BIAS_OV_WARN_LIMIT);
+	default:
+		return -ENODATA;
+	}
+}
+
+static int lt3074_write_word_data(struct i2c_client *client, int page,
+				  int reg, u16 word)
+{
+	switch (reg) {
+	case PMBUS_VIRT_VMON_UV_WARN_LIMIT:
+		return pmbus_write_word_data(client, 0,
+					    LT3074_MFR_BIAS_UV_WARN_LIMIT,
+					    word);
+	case PMBUS_VIRT_VMON_OV_WARN_LIMIT:
+		return pmbus_write_word_data(client, 0,
+					    LT3074_MFR_BIAS_OV_WARN_LIMIT,
+					    word);
+	default:
+		return -ENODATA;
+	}
+}
+
+static struct pmbus_driver_info lt3074_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_TEMPERATURE] = linear,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+		   PMBUS_HAVE_TEMP | PMBUS_HAVE_VMON |
+		   PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_STATUS_IOUT |
+		   PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
+	.read_word_data = lt3074_read_word_data,
+	.write_word_data = lt3074_write_word_data,
+#if IS_ENABLED(CONFIG_SENSORS_LT3074_REGULATOR)
+	.num_regulators = 1,
+	.reg_desc = lt3074_reg_desc,
+#endif
+};
+
+static int lt3074_probe(struct i2c_client *client)
+{
+	int ret;
+	struct device *dev = &client->dev;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENODEV;
+
+	ret = i2c_smbus_read_word_data(client, LT3074_MFR_SPECIAL_ID);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read ID\n");
+
+	if (ret != LT3074_SPECIAL_ID_VALUE)
+		return dev_err_probe(dev, -ENODEV, "ID mismatch\n");
+
+	return pmbus_do_probe(client, &lt3074_info);
+}
+
+static const struct i2c_device_id lt3074_id[] = {
+	{ "lt3074", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, lt3074_id);
+
+static const struct of_device_id __maybe_unused lt3074_of_match[] = {
+	{ .compatible = "adi,lt3074" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, lt3074_of_match);
+
+static struct i2c_driver lt3074_driver = {
+	.driver = {
+		.name = "lt3074",
+		.of_match_table = of_match_ptr(lt3074_of_match),
+	},
+	.probe = lt3074_probe,
+	.id_table = lt3074_id,
+};
+module_i2c_driver(lt3074_driver);
+
+MODULE_AUTHOR("Cedric Encarnacion <cedricjustine.encarnacion@analog.com>");
+MODULE_DESCRIPTION("PMBus driver for Analog Devices LT3074");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");