Commit 3bcfa9e4 authored by Herbert Valerio Riedel's avatar Herbert Valerio Riedel Committed by Linus Torvalds
Browse files

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: default avatarMartin Michlmayr <>
Signed-off-by: default avatarHerbert Valerio Riedel <>
Signed-off-by: default avatarMatthew Palmer <>
Signed-off-by: default avatarLaurie Bradshaw <>
Signed-off-by: default avatarMartin Michlmayr <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 6260a4b0
Kernel driver g760a
Supported chips:
* Global Mixed-mode Technology Inc. G760A
Prefix: 'g760a'
Datasheet: Publicly available at the GMT website
Author: Herbert Valerio Riedel <>
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.
......@@ -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
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
......@@ -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
g760a - Driver for the Global Mixed-mode Technology Inc. G760A
fan speed PWM controller chip
Copyright (C) 2007 Herbert Valerio Riedel <>
Complete datasheet is available at GMT's website:
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 */
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);
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;
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;
if (!(data->fan_sta & G760A_REG_FAN_STA_RPM_LOW))
rpm = rpm_from_cnt(data->act_cnt, data->clk, data->fan_div);
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;
data->set_cnt = PWM_TO_CNT(SENSORS_LIMIT(val, 0, 255));
g760a_write_value(client, G760A_REG_SET_CNT, data->set_cnt);
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[] = {
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,
return -EIO;
data = kzalloc(sizeof(struct g760a_data), GFP_KERNEL);
if (!data)
return -ENOMEM;
i2c_set_clientdata(client, data);
data->client = client;
/* 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;
sysfs_remove_group(&client->dev.kobj, &g760a_group);
i2c_set_clientdata(client, NULL);
return err;
static int g760a_remove(struct i2c_client *client)
struct g760a_data *data = i2c_get_clientdata(client);
sysfs_remove_group(&client->dev.kobj, &g760a_group);
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)
MODULE_AUTHOR("Herbert Valerio Riedel <>");
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