hwmon: add support for GMT G760A fan speed PWM controller

This controller can be found on the D-Link DNS-323 for instance, where
it is to be configured via static i2c_board_info in the board-specific
mach-orion/dns323-setup.c; this driver supports only the new-style
driver model.
Tested-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Signed-off-by: Matthew Palmer <mpalmer@debian.org>
Signed-off-by: Laurie Bradshaw <bradshaw.laurie@googlemail.com>
Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/hwmon/g760a

+Kernel driver g760a
+===================
+
+Supported chips:
+  * Global Mixed-mode Technology Inc. G760A
+    Prefix: 'g760a'
+    Datasheet: Publicly available at the GMT website
+      http://www.gmt.com.tw/datasheet/g760a.pdf
+
+Author: Herbert Valerio Riedel <hvr@gnu.org>
+
+Description
+-----------
+
+The GMT G760A Fan Speed PWM Controller is connected directly to a fan
+and performs closed-loop control of the fan speed.
+
+The fan speed is programmed by setting the period via 'pwm1' of two
+consecutive speed pulses. The period is defined in terms of clock
+cycle counts of an assumed 32kHz clock source.
+
+Setting a period of 0 stops the fan; setting the period to 255 sets
+fan to maximum speed.
+
+The measured fan rotation speed returned via 'fan1_input' is derived
+from the measured speed pulse period by assuming again a 32kHz clock
+source and a 2 pulse-per-revolution fan.
+
+The 'alarms' file provides access to the two alarm bits provided by
+the G760A chip's status register: Bit 0 is set when the actual fan
+speed differs more than 20% with respect to the programmed fan speed;
+bit 1 is set when fan speed is below 1920 RPM.
+
+The g760a driver will not update its values more frequently than every
+other second; reading them more often will do no harm, but will return
+'old' values.

drivers/hwmon/Kconfig

@@ -358,6 +358,16 @@ config SENSORS_FSCHMD
 	  This driver can also be built as a module.  If so, the module
 	  will be called fschmd.
 
+config SENSORS_G760A
+	tristate "GMT G760A"
+	depends on I2C
+	help
+	  If you say yes here you get support for Global Mixed-mode
+	  Technology Inc G760A fan speed PWM controller chips.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called g760a.
+
 config SENSORS_GL518SM
 	tristate "Genesys Logic GL518SM"
 	depends on I2C

drivers/hwmon/Makefile

@@ -42,6 +42,7 @@ obj-$(CONFIG_SENSORS_F75375S)	+= f75375s.o
 obj-$(CONFIG_SENSORS_FSCHER)	+= fscher.o
 obj-$(CONFIG_SENSORS_FSCHMD)	+= fschmd.o
 obj-$(CONFIG_SENSORS_FSCPOS)	+= fscpos.o
+obj-$(CONFIG_SENSORS_G760A)	+= g760a.o
 obj-$(CONFIG_SENSORS_GL518SM)	+= gl518sm.o
 obj-$(CONFIG_SENSORS_GL520SM)	+= gl520sm.o
 obj-$(CONFIG_SENSORS_ULTRA45)	+= ultra45_env.o

drivers/hwmon/g760a.c

+/*
+    g760a - Driver for the Global Mixed-mode Technology Inc. G760A
+            fan speed PWM controller chip
+
+    Copyright (C) 2007  Herbert Valerio Riedel <hvr@gnu.org>
+
+    Complete datasheet is available at GMT's website:
+      http://www.gmt.com.tw/datasheet/g760a.pdf
+
+    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/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+
+static const struct i2c_device_id g760a_id[] = {
+	{ "g760a", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, g760a_id);
+
+enum g760a_regs {
+	G760A_REG_SET_CNT = 0x00,
+	G760A_REG_ACT_CNT = 0x01,
+	G760A_REG_FAN_STA = 0x02
+};
+
+#define G760A_REG_FAN_STA_RPM_OFF 0x1 /* +/-20% off */
+#define G760A_REG_FAN_STA_RPM_LOW 0x2 /* below 1920rpm */
+
+/* register data is read (and cached) at most once per second */
+#define G760A_UPDATE_INTERVAL (HZ)
+
+struct g760a_data {
+	struct i2c_client *client;
+	struct device *hwmon_dev;
+	struct mutex update_lock;
+
+	/* board specific parameters */
+	u32 clk; /* default 32kHz */
+	u16 fan_div; /* default P=2 */
+
+	/* g760a register cache */
+	unsigned int valid:1;
+	unsigned long last_updated; /* In jiffies */
+
+	u8 set_cnt; /* PWM (period) count number; 0xff stops fan */
+	u8 act_cnt; /*   formula: cnt = (CLK * 30)/(rpm * P) */
+	u8 fan_sta; /* bit 0: set when actual fan speed more than 20%
+		     *   outside requested fan speed
+		     * bit 1: set when fan speed below 1920 rpm */
+};
+
+#define G760A_DEFAULT_CLK 32768
+#define G760A_DEFAULT_FAN_DIV 2
+
+#define PWM_FROM_CNT(cnt)	(0xff-(cnt))
+#define PWM_TO_CNT(pwm)		(0xff-(pwm))
+
+unsigned int rpm_from_cnt(u8 val, u32 clk, u16 div)
+{
+	return ((val == 0x00) ? 0 : ((clk*30)/(val*div)));
+}
+
+/* new-style driver model */
+static int g760a_probe(struct i2c_client *client,
+			const struct i2c_device_id *id);
+static int g760a_remove(struct i2c_client *client);
+
+static struct i2c_driver g760a_driver = {
+	.driver = {
+		.name	= "g760a",
+	},
+	.probe	  = g760a_probe,
+	.remove	  = g760a_remove,
+	.id_table = g760a_id,
+};
+
+/* read/write wrappers */
+static int g760a_read_value(struct i2c_client *client, enum g760a_regs reg)
+{
+	return i2c_smbus_read_byte_data(client, reg);
+}
+
+static int g760a_write_value(struct i2c_client *client, enum g760a_regs reg,
+			     u16 value)
+{
+	return i2c_smbus_write_byte_data(client, reg, value);
+}
+
+/****************************************************************************
+ * sysfs attributes
+ */
+
+static struct g760a_data *g760a_update_client(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct g760a_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated + G760A_UPDATE_INTERVAL)
+	    || !data->valid) {
+		dev_dbg(&client->dev, "Starting g760a update\n");
+
+		data->set_cnt = g760a_read_value(client, G760A_REG_SET_CNT);
+		data->act_cnt = g760a_read_value(client, G760A_REG_ACT_CNT);
+		data->fan_sta = g760a_read_value(client, G760A_REG_FAN_STA);
+
+		data->last_updated = jiffies;
+		data->valid = 1;
+	}
+
+	mutex_unlock(&data->update_lock);
+
+	return data;
+}
+
+static ssize_t show_fan(struct device *dev, struct device_attribute *da,
+			char *buf)
+{
+	struct g760a_data *data = g760a_update_client(dev);
+	unsigned int rpm = 0;
+
+	mutex_lock(&data->update_lock);
+	if (!(data->fan_sta & G760A_REG_FAN_STA_RPM_LOW))
+		rpm = rpm_from_cnt(data->act_cnt, data->clk, data->fan_div);
+	mutex_unlock(&data->update_lock);
+
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t show_fan_alarm(struct device *dev, struct device_attribute *da,
+			      char *buf)
+{
+	struct g760a_data *data = g760a_update_client(dev);
+
+	int fan_alarm = (data->fan_sta & G760A_REG_FAN_STA_RPM_OFF) ? 1 : 0;
+
+	return sprintf(buf, "%d\n", fan_alarm);
+}
+
+static ssize_t get_pwm(struct device *dev, struct device_attribute *da,
+		       char *buf)
+{
+	struct g760a_data *data = g760a_update_client(dev);
+
+	return sprintf(buf, "%d\n", PWM_FROM_CNT(data->set_cnt));
+}
+
+static ssize_t set_pwm(struct device *dev, struct device_attribute *da,
+		       const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct g760a_data *data = g760a_update_client(dev);
+	unsigned long val;
+
+	if (strict_strtoul(buf, 10, &val))
+		return -EINVAL;
+
+	mutex_lock(&data->update_lock);
+	data->set_cnt = PWM_TO_CNT(SENSORS_LIMIT(val, 0, 255));
+	g760a_write_value(client, G760A_REG_SET_CNT, data->set_cnt);
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+static DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
+static DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL);
+static DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL);
+
+static struct attribute *g760a_attributes[] = {
+	&dev_attr_pwm1.attr,
+	&dev_attr_fan1_input.attr,
+	&dev_attr_fan1_alarm.attr,
+	NULL
+};
+
+static const struct attribute_group g760a_group = {
+	.attrs = g760a_attributes,
+};
+
+/****************************************************************************
+ * new-style driver model code
+ */
+
+static int g760a_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct g760a_data *data;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	data = kzalloc(sizeof(struct g760a_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	/* setup default configuration for now */
+	data->fan_div = G760A_DEFAULT_FAN_DIV;
+	data->clk = G760A_DEFAULT_CLK;
+
+	/* Register sysfs hooks */
+	err = sysfs_create_group(&client->dev.kobj, &g760a_group);
+	if (err)
+		goto error_sysfs_create_group;
+
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		err = PTR_ERR(data->hwmon_dev);
+		goto error_hwmon_device_register;
+	}
+
+	return 0;
+
+error_hwmon_device_register:
+	sysfs_remove_group(&client->dev.kobj, &g760a_group);
+error_sysfs_create_group:
+	kfree(data);
+	i2c_set_clientdata(client, NULL);
+
+	return err;
+}
+
+static int g760a_remove(struct i2c_client *client)
+{
+	struct g760a_data *data = i2c_get_clientdata(client);
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &g760a_group);
+	kfree(data);
+	i2c_set_clientdata(client, NULL);
+
+	return 0;
+}
+
+/* module management */
+
+static int __init g760a_init(void)
+{
+	return i2c_add_driver(&g760a_driver);
+}
+
+static void __exit g760a_exit(void)
+{
+	i2c_del_driver(&g760a_driver);
+}
+
+MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
+MODULE_DESCRIPTION("GMT G760A driver");
+MODULE_LICENSE("GPL");
+
+module_init(g760a_init);
+module_exit(g760a_exit);