hwmon: (pmbus) Add support for MAX20751

MAX20751 is a multiphase power controller with internal buck converter.
It uses VR12.0 to report the output voltage. This requires an explicit
driver, since the VR version can not be auto-detected.

The chip supports a manufacturer specific command to fine-tune the output
voltage.  This command is not currently supported.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/max20751.c

@@ -0,0 +1,64 @@
+/*
+ * Hardware monitoring driver for Maxim MAX20751
+ *
+ * Copyright (c) 2015 Guenter Roeck
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include "pmbus.h"
+
+static struct pmbus_driver_info max20751_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = vid,
+	.vrm_version = vr12,
+	.format[PSC_TEMPERATURE] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_POWER] = linear,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP |
+		PMBUS_HAVE_POUT,
+};
+
+static int max20751_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	return pmbus_do_probe(client, id, &max20751_info);
+}
+
+static const struct i2c_device_id max20751_id[] = {
+	{"max20751", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, max20751_id);
+
+static struct i2c_driver max20751_driver = {
+	.driver = {
+		   .name = "max20751",
+		   },
+	.probe = max20751_probe,
+	.remove = pmbus_do_remove,
+	.id_table = max20751_id,
+};
+
+module_i2c_driver(max20751_driver);
+
+MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
+MODULE_DESCRIPTION("PMBus driver for Maxim MAX20751");
+MODULE_LICENSE("GPL");