hwmon: pmbus: Add support for Sony APS-379

Add pmbus support for Sony APS-379 power supplies. There are a few PMBUS
commands that return data that is undocumented/invalid so these need to
be rejected with -ENXIO. The READ_VOUT command returns data in linear11
format instead of linear16 so we need to workaround this.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20260410012414.2818829-3-chris.packham@alliedtelesis.co.nz
[groeck: Dropped empty line from documentation; added module name to Kconfig]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 165 insertions, 0 deletions

diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index a4513fc6bc26..db63acbe08c8 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -77,6 +77,15 @@ config SENSORS_ADP1050_REGULATOR
 	  µModule regulators that can provide microprocessor power from 54V
 	  power distribution architecture.
 
+config SENSORS_APS_379
+	tristate "Sony APS-379 Power Supplies"
+	help
+	  If you say yes here you get hardware monitoring support for Sony
+	  APS-379 Power Supplies.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called aps-379.
+
 config SENSORS_BEL_PFE
 	tristate "Bel PFE Compatible Power Supplies"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index d592d8c77bec..63a9870c7b53 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_SENSORS_ACBEL_FSG032) += acbel-fsg032.o
 obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
 obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
 obj-$(CONFIG_SENSORS_ADP1050)	+= adp1050.o
+obj-$(CONFIG_SENSORS_APS_379)	+= aps-379.o
 obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
 obj-$(CONFIG_SENSORS_BPA_RS600)	+= bpa-rs600.o
 obj-$(CONFIG_SENSORS_DELTA_AHE50DC_FAN) += delta-ahe50dc-fan.o
diff --git a/drivers/hwmon/pmbus/aps-379.c b/drivers/hwmon/pmbus/aps-379.c
new file mode 100644
index 000000000000..7d46cd647e20
--- /dev/null
+++ b/drivers/hwmon/pmbus/aps-379.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for Sony APS-379 Power Supplies
+ *
+ * Copyright 2026 Allied Telesis Labs
+ */
+
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pmbus.h>
+#include "pmbus.h"
+
+/*
+ * The VOUT format used by the chip is linear11, not linear16. Provide a hard
+ * coded VOUT_MODE that says VOUT is in linear mode with a fixed exponent of
+ * 2^-4.
+ */
+#define APS_379_VOUT_MODE ((u8)(-4 & 0x1f))
+
+static int aps_379_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		return APS_379_VOUT_MODE;
+	default:
+		return -ENODATA;
+	}
+}
+
+/*
+ * The APS-379 uses linear11 format instead of linear16. We've reported the exponent
+ * via the PMBUS_VOUT_MODE so we just return the mantissa here.
+ */
+static int aps_379_read_vout(struct i2c_client *client)
+{
+	int ret;
+
+	ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_READ_VOUT);
+	if (ret < 0)
+		return ret;
+
+	return clamp_val(sign_extend32(ret & 0x7ff, 10), 0, 0x3ff);
+}
+
+static int aps_379_read_word_data(struct i2c_client *client, int page, int phase, int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_UV_WARN_LIMIT:
+	case PMBUS_VOUT_OV_WARN_LIMIT:
+	case PMBUS_VOUT_UV_FAULT_LIMIT:
+	case PMBUS_VOUT_OV_FAULT_LIMIT:
+	case PMBUS_IOUT_OC_WARN_LIMIT:
+	case PMBUS_IOUT_UC_FAULT_LIMIT:
+	case PMBUS_UT_WARN_LIMIT:
+	case PMBUS_UT_FAULT_LIMIT:
+	case PMBUS_OT_WARN_LIMIT:
+	case PMBUS_OT_FAULT_LIMIT:
+	case PMBUS_PIN_OP_WARN_LIMIT:
+	case PMBUS_POUT_OP_WARN_LIMIT:
+	case PMBUS_MFR_IIN_MAX:
+	case PMBUS_MFR_PIN_MAX:
+	case PMBUS_MFR_VOUT_MIN:
+	case PMBUS_MFR_VOUT_MAX:
+	case PMBUS_MFR_IOUT_MAX:
+	case PMBUS_MFR_POUT_MAX:
+	case PMBUS_MFR_MAX_TEMP_1:
+		/* These commands return data but it is invalid/un-documented */
+		return -ENXIO;
+	case PMBUS_IOUT_OC_FAULT_LIMIT:
+		/*
+		 * The standard requires this to be a value in Amps but it's
+		 * actually a percentage of the rated output (123A for
+		 * 110-240Vac, 110A for 90-100Vac) which we don't know. Ignore
+		 * it rather than guessing.
+		 */
+		return -ENXIO;
+	case PMBUS_READ_VOUT:
+		return aps_379_read_vout(client);
+	default:
+		return -ENODATA;
+	}
+}
+
+static struct pmbus_driver_info aps_379_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_OUT] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_POWER] = linear,
+	.format[PSC_TEMPERATURE] = linear,
+	.format[PSC_FAN] = linear,
+	.func[0] = PMBUS_HAVE_VOUT |
+		PMBUS_HAVE_IOUT |
+		PMBUS_HAVE_PIN | PMBUS_HAVE_POUT |
+		PMBUS_HAVE_TEMP |
+		PMBUS_HAVE_FAN12,
+	.read_byte_data = aps_379_read_byte_data,
+	.read_word_data = aps_379_read_word_data,
+};
+
+static const struct i2c_device_id aps_379_id[] = {
+	{ "aps-379", 0 },
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, aps_379_id);
+
+static int aps_379_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = { 0 };
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_BYTE_DATA
+				     | I2C_FUNC_SMBUS_READ_WORD_DATA
+				     | I2C_FUNC_SMBUS_READ_BLOCK_DATA))
+		return -ENODEV;
+
+	ret = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read Manufacturer Model\n");
+		return ret;
+	}
+
+	if (strncasecmp(buf, aps_379_id[0].name, strlen(aps_379_id[0].name)) != 0) {
+		buf[ret] = '\0';
+		dev_err(dev, "Unsupported Manufacturer Model '%s'\n", buf);
+		return -ENODEV;
+	}
+
+	return pmbus_do_probe(client, &aps_379_info);
+}
+
+static const struct of_device_id __maybe_unused aps_379_of_match[] = {
+	{ .compatible = "sony,aps-379" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, aps_379_of_match);
+
+static struct i2c_driver aps_379_driver = {
+	.driver = {
+		.name = "aps-379",
+		.of_match_table = of_match_ptr(aps_379_of_match),
+	},
+	.probe = aps_379_probe,
+	.id_table = aps_379_id,
+};
+
+module_i2c_driver(aps_379_driver);
+
+MODULE_AUTHOR("Chris Packham");
+MODULE_DESCRIPTION("PMBus driver for Sony APS-379");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");