diff --git a/Documentation/hwmon/fsp-3y.rst b/Documentation/hwmon/fsp-3y.rst
new file mode 100644
index 000000000000..5693d83a2035
--- /dev/null
+++ b/Documentation/hwmon/fsp-3y.rst
@@ -0,0 +1,28 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver fsp3y
+======================
+Supported devices:
+  * 3Y POWER YH-5151E
+  * 3Y POWER YM-2151E
+
+Author: Václav Kubernát <kubernat@cesnet.cz>
+
+Description
+-----------
+This driver implements limited support for two 3Y POWER devices.
+
+Sysfs entries
+-------------
+  * in1_input            input voltage
+  * in2_input            12V output voltage
+  * in3_input            5V output voltage
+  * curr1_input          input current
+  * curr2_input          12V output current
+  * curr3_input          5V output current
+  * fan1_input           fan rpm
+  * temp1_input          temperature 1
+  * temp2_input          temperature 2
+  * temp3_input          temperature 3
+  * power1_input         input power
+  * power2_input         output power
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index fcb870ce6286..55c9f014c248 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -63,6 +63,7 @@ Hardware Monitoring Kernel Drivers
    f71805f
    f71882fg
    fam15h_power
+   fsp-3y
    ftsteutates
    g760a
    g762
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 03606d4298a4..9d12d446396c 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -56,6 +56,16 @@ config SENSORS_BEL_PFE
 	  This driver can also be built as a module. If so, the module will
 	  be called bel-pfe.
 
+config SENSORS_FSP_3Y
+	tristate "FSP/3Y-Power power supplies"
+	help
+	  If you say yes here you get hardware monitoring support for
+	  FSP/3Y-Power hot-swap power supplies.
+	  Supported models: YH-5151E, YM-2151E
+
+	  This driver can also be built as a module. If so, the module will
+	  be called fsp-3y.
+
 config SENSORS_IBM_CFFPS
 	tristate "IBM Common Form Factor Power Supply"
 	depends on LEDS_CLASS
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 6a4ba0fdc1db..bfe218ad898f 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_SENSORS_PMBUS)	+= pmbus.o
 obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
 obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
 obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
+obj-$(CONFIG_SENSORS_FSP_3Y)	+= fsp-3y.o
 obj-$(CONFIG_SENSORS_IBM_CFFPS)	+= ibm-cffps.o
 obj-$(CONFIG_SENSORS_INSPUR_IPSPS) += inspur-ipsps.o
 obj-$(CONFIG_SENSORS_IR35221)	+= ir35221.o
diff --git a/drivers/hwmon/pmbus/fsp-3y.c b/drivers/hwmon/pmbus/fsp-3y.c
new file mode 100644
index 000000000000..564649e87e34
--- /dev/null
+++ b/drivers/hwmon/pmbus/fsp-3y.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for FSP 3Y-Power PSUs
+ *
+ * Copyright (c) 2021 Václav Kubernát, CESNET
+ *
+ * This driver is mostly reverse engineered with the help of a tool called pmbus_peek written by
+ * David Brownell (and later adopted by Jan Kundrát). The device has some sort of a timing issue
+ * when switching pages, details are explained in the code. The driver support is limited. It
+ * exposes only the values, that have been tested to work correctly. Unsupported values either
+ * aren't supported by the devices or their encondings are unknown.
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include "pmbus.h"
+
+#define YM2151_PAGE_12V_LOG	0x00
+#define YM2151_PAGE_12V_REAL	0x00
+#define YM2151_PAGE_5VSB_LOG	0x01
+#define YM2151_PAGE_5VSB_REAL	0x20
+#define YH5151E_PAGE_12V_LOG	0x00
+#define YH5151E_PAGE_12V_REAL	0x00
+#define YH5151E_PAGE_5V_LOG	0x01
+#define YH5151E_PAGE_5V_REAL	0x10
+#define YH5151E_PAGE_3V3_LOG	0x02
+#define YH5151E_PAGE_3V3_REAL	0x11
+
+enum chips {
+	ym2151e,
+	yh5151e
+};
+
+struct fsp3y_data {
+	struct pmbus_driver_info info;
+	int chip;
+	int page;
+};
+
+#define to_fsp3y_data(x) container_of(x, struct fsp3y_data, info)
+
+static int page_log_to_page_real(int page_log, enum chips chip)
+{
+	switch (chip) {
+	case ym2151e:
+		switch (page_log) {
+		case YM2151_PAGE_12V_LOG:
+			return YM2151_PAGE_12V_REAL;
+		case YM2151_PAGE_5VSB_LOG:
+			return YM2151_PAGE_5VSB_REAL;
+		}
+		return -EINVAL;
+	case yh5151e:
+		switch (page_log) {
+		case YH5151E_PAGE_12V_LOG:
+			return YH5151E_PAGE_12V_REAL;
+		case YH5151E_PAGE_5V_LOG:
+			return YH5151E_PAGE_5V_LOG;
+		case YH5151E_PAGE_3V3_LOG:
+			return YH5151E_PAGE_3V3_REAL;
+		}
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static int set_page(struct i2c_client *client, int page_log)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct fsp3y_data *data = to_fsp3y_data(info);
+	int rv;
+	int page_real;
+
+	if (page_log < 0)
+		return 0;
+
+	page_real = page_log_to_page_real(page_log, data->chip);
+	if (page_real < 0)
+		return page_real;
+
+	if (data->page != page_real) {
+		rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page_real);
+		if (rv < 0)
+			return rv;
+
+		data->page = page_real;
+
+		/*
+		 * Testing showed that the device has a timing issue. After
+		 * setting a page, it takes a while, before the device actually
+		 * gives the correct values from the correct page. 20 ms was
+		 * tested to be enough to not give wrong values (15 ms wasn't
+		 * enough).
+		 */
+		usleep_range(20000, 30000);
+	}
+
+	return 0;
+}
+
+static int fsp3y_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	int rv;
+
+	rv = set_page(client, page);
+	if (rv < 0)
+		return rv;
+
+	return i2c_smbus_read_byte_data(client, reg);
+}
+
+static int fsp3y_read_word_data(struct i2c_client *client, int page, int phase, int reg)
+{
+	int rv;
+
+	/*
+	 * This masks commands which weren't tested to work correctly. Some of
+	 * the masked commands return 0xFFFF. These would probably get tagged as
+	 * invalid by pmbus_core. Other ones do return values which might be
+	 * useful (that is, they are not 0xFFFF), but their encoding is unknown,
+	 * and so they are unsupported.
+	 */
+	switch (reg) {
+	case PMBUS_READ_FAN_SPEED_1:
+	case PMBUS_READ_IIN:
+	case PMBUS_READ_IOUT:
+	case PMBUS_READ_PIN:
+	case PMBUS_READ_POUT:
+	case PMBUS_READ_TEMPERATURE_1:
+	case PMBUS_READ_TEMPERATURE_2:
+	case PMBUS_READ_TEMPERATURE_3:
+	case PMBUS_READ_VIN:
+	case PMBUS_READ_VOUT:
+	case PMBUS_STATUS_WORD:
+		break;
+	default:
+		return -ENXIO;
+	}
+
+	rv = set_page(client, page);
+	if (rv < 0)
+		return rv;
+
+	return i2c_smbus_read_word_data(client, reg);
+}
+
+struct pmbus_driver_info fsp3y_info[] = {
+	[ym2151e] = {
+		.pages = 2,
+		.func[YM2151_PAGE_12V_LOG] =
+			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+			PMBUS_HAVE_PIN | PMBUS_HAVE_POUT  |
+			PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 |
+			PMBUS_HAVE_VIN | PMBUS_HAVE_IIN |
+			PMBUS_HAVE_FAN12,
+		.func[YM2151_PAGE_5VSB_LOG] =
+			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT,
+			PMBUS_HAVE_IIN,
+		.read_word_data = fsp3y_read_word_data,
+		.read_byte_data = fsp3y_read_byte_data,
+	},
+	[yh5151e] = {
+		.pages = 3,
+		.func[YH5151E_PAGE_12V_LOG] =
+			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+			PMBUS_HAVE_POUT  |
+			PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3,
+		.func[YH5151E_PAGE_5V_LOG] =
+			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+			PMBUS_HAVE_POUT,
+		.func[YH5151E_PAGE_3V3_LOG] =
+			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+			PMBUS_HAVE_POUT,
+		.read_word_data = fsp3y_read_word_data,
+		.read_byte_data = fsp3y_read_byte_data,
+	}
+};
+
+static int fsp3y_detect(struct i2c_client *client)
+{
+	int rv;
+	u8 buf[I2C_SMBUS_BLOCK_MAX + 1];
+
+	rv = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
+	if (rv < 0)
+		return rv;
+
+	buf[rv] = '\0';
+
+	if (rv == 8) {
+		if (!strcmp(buf, "YM-2151E"))
+			return ym2151e;
+		else if (!strcmp(buf, "YH-5151E"))
+			return yh5151e;
+	}
+
+	dev_err(&client->dev, "Unsupported model %.*s\n", rv, buf);
+	return -ENODEV;
+}
+
+static const struct i2c_device_id fsp3y_id[] = {
+	{"ym2151e", ym2151e},
+	{"yh5151e", yh5151e},
+	{0}
+};
+
+static int fsp3y_probe(struct i2c_client *client)
+{
+	struct fsp3y_data *data;
+	const struct i2c_device_id *id;
+	int rv;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct fsp3y_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->chip = fsp3y_detect(client);
+	if (data->chip < 0)
+		return data->chip;
+
+	id = i2c_match_id(fsp3y_id, client);
+	if (data->chip != id->driver_data)
+		dev_warn(&client->dev, "Device mismatch: Configured %s (%d), detected %d\n",
+			 id->name, (int)id->driver_data, data->chip);
+
+	rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
+	if (rv < 0)
+		return rv;
+	data->page = rv;
+
+	data->info = fsp3y_info[data->chip];
+
+	return pmbus_do_probe(client, &data->info);
+}
+
+MODULE_DEVICE_TABLE(i2c, fsp3y_id);
+
+static struct i2c_driver fsp3y_driver = {
+	.driver = {
+		   .name = "fsp3y",
+		   },
+	.probe_new = fsp3y_probe,
+	.id_table = fsp3y_id
+};
+
+module_i2c_driver(fsp3y_driver);
+
+MODULE_AUTHOR("Václav Kubernát");
+MODULE_DESCRIPTION("PMBus driver for FSP/3Y-Power power supplies");
+MODULE_LICENSE("GPL");
