hwmon: (pmbus) Add Delta AHE-50DC fan control module driver

This device is an integrated module of the Delta AHE-50DC Open19 power
shelf.  I haven't been able to procure any proper documentation for
it, but it seems to be a (somewhat minimally) PMBus-compliant device.
It provides four fan speeds, four temperatures (three standard and one
manufacturer-specific via a virtual second page), and a vin reading.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20211208213703.2577-2-zev@bewilderbeest.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

MAINTAINERS

@@ -5436,6 +5436,12 @@ W:	https://linuxtv.org
 T:	git git://linuxtv.org/media_tree.git
 F:	drivers/media/platform/sti/delta
 
+DELTA AHE-50DC FAN CONTROL MODULE DRIVER
+M:	Zev Weiss <zev@bewilderbeest.net>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	drivers/hwmon/pmbus/delta-ahe50dc-fan.c
+
 DELTA DPS920AB PSU DRIVER
 M:	Robert Marko <robert.marko@sartura.hr>
 L:	linux-hwmon@vger.kernel.org

drivers/hwmon/pmbus/Kconfig

@@ -66,6 +66,16 @@ config SENSORS_BPA_RS600
 	  This driver can also be built as a module. If so, the module will
 	  be called bpa-rs600.
 
+config SENSORS_DELTA_AHE50DC_FAN
+	tristate "Delta AHE-50DC fan control module"
+	help
+	  If you say yes here you get hardware monitoring support for
+	  the integrated fan control module of the Delta AHE-50DC
+	  Open19 power shelf.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called delta-ahe50dc-fan.
+
 config SENSORS_FSP_3Y
 	tristate "FSP/3Y-Power power supplies"
 	help

drivers/hwmon/pmbus/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
 obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
 obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
 obj-$(CONFIG_SENSORS_BPA_RS600)	+= bpa-rs600.o
+obj-$(CONFIG_SENSORS_DELTA_AHE50DC_FAN) += delta-ahe50dc-fan.o
 obj-$(CONFIG_SENSORS_FSP_3Y)	+= fsp-3y.o
 obj-$(CONFIG_SENSORS_IBM_CFFPS)	+= ibm-cffps.o
 obj-$(CONFIG_SENSORS_DPS920AB)	+= dps920ab.o

drivers/hwmon/pmbus/delta-ahe50dc-fan.c

@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Delta AHE-50DC power shelf fan control module driver
+ *
+ * Copyright 2021 Zev Weiss <zev@bewilderbeest.net>
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pmbus.h>
+
+#include "pmbus.h"
+
+#define AHE50DC_PMBUS_READ_TEMP4 0xd0
+
+static int ahe50dc_fan_read_word_data(struct i2c_client *client, int page, int phase, int reg)
+{
+	/* temp1 in (virtual) page 1 is remapped to mfr-specific temp4 */
+	if (page == 1) {
+		if (reg == PMBUS_READ_TEMPERATURE_1)
+			return i2c_smbus_read_word_data(client, AHE50DC_PMBUS_READ_TEMP4);
+		return -EOPNOTSUPP;
+	}
+
+	/*
+	 * There's a fairly limited set of commands this device actually
+	 * supports, so here we block attempts to read anything else (which
+	 * return 0xffff and would cause confusion elsewhere).
+	 */
+	switch (reg) {
+	case PMBUS_STATUS_WORD:
+	case PMBUS_FAN_COMMAND_1:
+	case PMBUS_FAN_COMMAND_2:
+	case PMBUS_FAN_COMMAND_3:
+	case PMBUS_FAN_COMMAND_4:
+	case PMBUS_STATUS_FAN_12:
+	case PMBUS_STATUS_FAN_34:
+	case PMBUS_READ_VIN:
+	case PMBUS_READ_TEMPERATURE_1:
+	case PMBUS_READ_TEMPERATURE_2:
+	case PMBUS_READ_TEMPERATURE_3:
+	case PMBUS_READ_FAN_SPEED_1:
+	case PMBUS_READ_FAN_SPEED_2:
+	case PMBUS_READ_FAN_SPEED_3:
+	case PMBUS_READ_FAN_SPEED_4:
+		return -ENODATA;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static struct pmbus_driver_info ahe50dc_fan_info = {
+	.pages = 2,
+	.format[PSC_FAN] = direct,
+	.format[PSC_TEMPERATURE] = direct,
+	.format[PSC_VOLTAGE_IN] = direct,
+	.m[PSC_FAN] = 1,
+	.b[PSC_FAN] = 0,
+	.R[PSC_FAN] = 0,
+	.m[PSC_TEMPERATURE] = 1,
+	.b[PSC_TEMPERATURE] = 0,
+	.R[PSC_TEMPERATURE] = 1,
+	.m[PSC_VOLTAGE_IN] = 1,
+	.b[PSC_VOLTAGE_IN] = 0,
+	.R[PSC_VOLTAGE_IN] = 3,
+	.func[0] = PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3 |
+		PMBUS_HAVE_VIN | PMBUS_HAVE_FAN12 | PMBUS_HAVE_FAN34 |
+		PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_STATUS_FAN34 | PMBUS_PAGE_VIRTUAL,
+	.func[1] = PMBUS_HAVE_TEMP | PMBUS_PAGE_VIRTUAL,
+	.read_word_data = ahe50dc_fan_read_word_data,
+};
+
+/*
+ * CAPABILITY returns 0xff, which appears to be this device's way indicating
+ * it doesn't support something (and if we enable I2C_CLIENT_PEC on seeing bit
+ * 7 being set it generates bad PECs, so let's not go there).
+ */
+static struct pmbus_platform_data ahe50dc_fan_data = {
+	.flags = PMBUS_NO_CAPABILITY,
+};
+
+static int ahe50dc_fan_probe(struct i2c_client *client)
+{
+	client->dev.platform_data = &ahe50dc_fan_data;
+	return pmbus_do_probe(client, &ahe50dc_fan_info);
+}
+
+static const struct i2c_device_id ahe50dc_fan_id[] = {
+	{ "ahe50dc_fan" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ahe50dc_fan_id);
+
+static const struct of_device_id __maybe_unused ahe50dc_fan_of_match[] = {
+	{ .compatible = "delta,ahe50dc-fan" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ahe50dc_fan_of_match);
+
+static struct i2c_driver ahe50dc_fan_driver = {
+	.driver = {
+		   .name = "ahe50dc_fan",
+		   .of_match_table = of_match_ptr(ahe50dc_fan_of_match),
+	},
+	.probe_new = ahe50dc_fan_probe,
+	.id_table = ahe50dc_fan_id,
+};
+module_i2c_driver(ahe50dc_fan_driver);
+
+MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
+MODULE_DESCRIPTION("Driver for Delta AHE-50DC power shelf fan control module");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(PMBUS);