hwmon: (pmbus/max20830) add driver for max20830

Add support for MAX20830 step-down DC-DC switching regulator with
PMBus interface. It allows monitoring of input/output voltage,
output current and temperature through the PMBus serial interface.

Signed-off-by: Alexis Czezar Torreno <alexisczezar.torreno@analog.com>
Link: https://lore.kernel.org/r/20260505-dev_max20830-v4-2-4343dcbfd7d7@analog.com
[groeck: checkpatch cleanup (space before and after '-')]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 120 insertions, 0 deletions

diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 1f99a333abc7..8708235e3c23 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -375,6 +375,15 @@ config SENSORS_MAX20751
 	  This driver can also be built as a module. If so, the module will
 	  be called max20751.
 
+config SENSORS_MAX20830
+	tristate "Analog Devices MAX20830"
+	help
+	  If you say yes here you get hardware monitoring support for Analog
+	  Devices MAX20830.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called max20830.
+
 config SENSORS_MAX31785
 	tristate "Maxim MAX31785 and compatibles"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 039848ecee7f..2820e7442e32 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_SENSORS_MAX16601)	+= max16601.o
 obj-$(CONFIG_SENSORS_MAX17616)	+= max17616.o
 obj-$(CONFIG_SENSORS_MAX20730)	+= max20730.o
 obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
+obj-$(CONFIG_SENSORS_MAX20830)	+= max20830.o
 obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
 obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
 obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
diff --git a/drivers/hwmon/pmbus/max20830.c b/drivers/hwmon/pmbus/max20830.c
new file mode 100644
index 000000000000..cb2c23672166
--- /dev/null
+++ b/drivers/hwmon/pmbus/max20830.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hardware monitoring driver for Analog Devices MAX20830
+ *
+ * Copyright (C) 2026 Analog Devices, Inc.
+ */
+
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include "pmbus.h"
+
+#define MAX20830_IC_DEVICE_ID_LENGTH	9
+
+static struct pmbus_driver_info max20830_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_STATUS_VOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
+};
+
+static int max20830_probe(struct i2c_client *client)
+{
+	u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = {};
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BLOCK_DATA) &&
+	    !i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
+		return -ENODEV;
+
+	/*
+	 * Use i2c_smbus_read_block_data() if supported, otherwise fall back
+	 * to i2c_smbus_read_i2c_block_data() to support I2C controllers
+	 * which do not support SMBus block reads.
+	 */
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BLOCK_DATA)) {
+		/* Reads 9 Data bytes from MAX20830 */
+		ret = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID, buf);
+		if (ret < 0)
+			return dev_err_probe(&client->dev, ret,
+					     "Failed to read IC_DEVICE_ID\n");
+	} else {
+		/* Reads 1 length byte + 9 Data bytes from MAX20830 */
+		ret = i2c_smbus_read_i2c_block_data(client, PMBUS_IC_DEVICE_ID,
+						    MAX20830_IC_DEVICE_ID_LENGTH + 1,
+						    buf);
+		if (ret < 0)
+			return dev_err_probe(&client->dev, ret,
+					     "Failed to read IC_DEVICE_ID\n");
+		/*
+		 * Moves data forward, removing the length byte, this is to
+		 * match the format of i2c_smbus_read_block_data().
+		 * Also adjust return value to reflect length byte removal.
+		 */
+		memmove(buf, buf + 1, MAX20830_IC_DEVICE_ID_LENGTH);
+		ret = ret - 1;
+	}
+
+	/*
+	 * MAX20830 IC_DEVICE_ID sends string data "MAX20830\0".
+	 * Return value should at least be 9 bytes of data.
+	 */
+	if (ret < MAX20830_IC_DEVICE_ID_LENGTH)
+		return dev_err_probe(&client->dev, -ENODEV,
+				     "IC_DEVICE_ID too short: expected at least 9 bytes, got %d\n",
+				     ret);
+
+	/* 9 bytes of data, buf[0]-buf[7] = "MAX20830", buf[8] = '\0' */
+	buf[MAX20830_IC_DEVICE_ID_LENGTH - 1] = '\0';
+	if (strncmp(buf, "MAX20830", MAX20830_IC_DEVICE_ID_LENGTH - 1))
+		return dev_err_probe(&client->dev, -ENODEV,
+				     "Unsupported device: '%s'\n", buf);
+
+	return pmbus_do_probe(client, &max20830_info);
+}
+
+static const struct i2c_device_id max20830_id[] = {
+	{"max20830"},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max20830_id);
+
+static const struct of_device_id max20830_of_match[] = {
+	{ .compatible = "adi,max20830" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max20830_of_match);
+
+static struct i2c_driver max20830_driver = {
+	.driver = {
+		.name = "max20830",
+		.of_match_table = max20830_of_match,
+	},
+	.probe = max20830_probe,
+	.id_table = max20830_id,
+};
+
+module_i2c_driver(max20830_driver);
+
+MODULE_AUTHOR("Alexis Czezar Torreno <alexisczezar.torreno@analog.com>");
+MODULE_DESCRIPTION("PMBus driver for Analog Devices MAX20830");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");