g760a.c

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/*
 * g760a - Driver for the Global Mixed-mode Technology Inc. G760A
 *     fan speed PWM controller chip
 *
 * Copyright (C) 2007  Herbert Valerio Riedel <[email protected]>
 *
 * Complete datasheet is available at GMT's website:
 * http://www.gmt.com.tw/product/datasheet/EDS-760A.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))

static inline 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 (kstrtoul(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 = devm_kzalloc(&client->dev, 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)
        return err;

    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);
    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);
    return 0;
}

module_i2c_driver(g760a_driver);

MODULE_AUTHOR("Herbert Valerio Riedel <[email protected]>");
MODULE_DESCRIPTION("GMT G760A driver");
MODULE_LICENSE("GPL");