pmbus: Add driver for Maxim MAX31785 Intelligent Fan Controller

The Maxim MAX31785 is a PMBus device providing closed-loop, multi-channel
fan management with temperature and remote voltage sensing. It supports
various fan control features, including PWM frequency control, temperature
hysteresis, dual tachometer measurements, and fan health monitoring.

This patch presents a basic driver using only the existing features of the
PMBus subsystem.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
[groeck: Modified description to clarify that fan control is not yet provided]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 116 insertions, 0 deletions

diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c
new file mode 100644
index 000000000000..9313849d5160
--- /dev/null
+++ b/drivers/hwmon/pmbus/max31785.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2017 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include "pmbus.h"
+
+enum max31785_regs {
+	MFR_REVISION		= 0x9b,
+};
+
+#define MAX31785_NR_PAGES		23
+
+#define MAX31785_FAN_FUNCS \
+	(PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12)
+
+#define MAX31785_TEMP_FUNCS \
+	(PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP)
+
+#define MAX31785_VOUT_FUNCS \
+	(PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT)
+
+static const struct pmbus_driver_info max31785_info = {
+	.pages = MAX31785_NR_PAGES,
+
+	/* RPM */
+	.format[PSC_FAN] = direct,
+	.m[PSC_FAN] = 1,
+	.b[PSC_FAN] = 0,
+	.R[PSC_FAN] = 0,
+	.func[0] = MAX31785_FAN_FUNCS,
+	.func[1] = MAX31785_FAN_FUNCS,
+	.func[2] = MAX31785_FAN_FUNCS,
+	.func[3] = MAX31785_FAN_FUNCS,
+	.func[4] = MAX31785_FAN_FUNCS,
+	.func[5] = MAX31785_FAN_FUNCS,
+
+	.format[PSC_TEMPERATURE] = direct,
+	.m[PSC_TEMPERATURE] = 1,
+	.b[PSC_TEMPERATURE] = 0,
+	.R[PSC_TEMPERATURE] = 2,
+	.func[6]  = MAX31785_TEMP_FUNCS,
+	.func[7]  = MAX31785_TEMP_FUNCS,
+	.func[8]  = MAX31785_TEMP_FUNCS,
+	.func[9]  = MAX31785_TEMP_FUNCS,
+	.func[10] = MAX31785_TEMP_FUNCS,
+	.func[11] = MAX31785_TEMP_FUNCS,
+	.func[12] = MAX31785_TEMP_FUNCS,
+	.func[13] = MAX31785_TEMP_FUNCS,
+	.func[14] = MAX31785_TEMP_FUNCS,
+	.func[15] = MAX31785_TEMP_FUNCS,
+	.func[16] = MAX31785_TEMP_FUNCS,
+
+	.format[PSC_VOLTAGE_OUT] = direct,
+	.m[PSC_VOLTAGE_OUT] = 1,
+	.b[PSC_VOLTAGE_OUT] = 0,
+	.R[PSC_VOLTAGE_OUT] = 0,
+	.func[17] = MAX31785_VOUT_FUNCS,
+	.func[18] = MAX31785_VOUT_FUNCS,
+	.func[19] = MAX31785_VOUT_FUNCS,
+	.func[20] = MAX31785_VOUT_FUNCS,
+	.func[21] = MAX31785_VOUT_FUNCS,
+	.func[22] = MAX31785_VOUT_FUNCS,
+};
+
+static int max31785_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct pmbus_driver_info *info;
+	s64 ret;
+
+	info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	*info = max31785_info;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 255);
+	if (ret < 0)
+		return ret;
+
+	return pmbus_do_probe(client, id, info);
+}
+
+static const struct i2c_device_id max31785_id[] = {
+	{ "max31785", 0 },
+	{ "max31785a", 0 },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(i2c, max31785_id);
+
+static struct i2c_driver max31785_driver = {
+	.driver = {
+		.name = "max31785",
+	},
+	.probe = max31785_probe,
+	.remove = pmbus_do_remove,
+	.id_table = max31785_id,
+};
+
+module_i2c_driver(max31785_driver);
+
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
+MODULE_DESCRIPTION("PMBus driver for the Maxim MAX31785");
+MODULE_LICENSE("GPL");