linux/drivers/hwmon/g760a.c
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   1/*
   2 * g760a - Driver for the Global Mixed-mode Technology Inc. G760A
   3 *         fan speed PWM controller chip
   4 *
   5 * Copyright (C) 2007  Herbert Valerio Riedel <hvr@gnu.org>
   6 *
   7 * Complete datasheet is available at GMT's website:
   8 * http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf
   9 *
  10 * This program is free software; you can redistribute it and/or modify
  11 * it under the terms of the GNU General Public License as published by
  12 * the Free Software Foundation; either version 2 of the License, or
  13 * (at your option) any later version.
  14 */
  15
  16#include <linux/module.h>
  17#include <linux/init.h>
  18#include <linux/slab.h>
  19#include <linux/jiffies.h>
  20#include <linux/i2c.h>
  21#include <linux/hwmon.h>
  22#include <linux/hwmon-sysfs.h>
  23#include <linux/err.h>
  24#include <linux/mutex.h>
  25#include <linux/sysfs.h>
  26
  27enum g760a_regs {
  28        G760A_REG_SET_CNT = 0x00,
  29        G760A_REG_ACT_CNT = 0x01,
  30        G760A_REG_FAN_STA = 0x02
  31};
  32
  33#define G760A_REG_FAN_STA_RPM_OFF 0x1 /* +/-20% off */
  34#define G760A_REG_FAN_STA_RPM_LOW 0x2 /* below 1920rpm */
  35
  36/* register data is read (and cached) at most once per second */
  37#define G760A_UPDATE_INTERVAL (HZ)
  38
  39struct g760a_data {
  40        struct i2c_client *client;
  41        struct mutex update_lock;
  42
  43        /* board specific parameters */
  44        u32 clk; /* default 32kHz */
  45        u16 fan_div; /* default P=2 */
  46
  47        /* g760a register cache */
  48        unsigned int valid:1;
  49        unsigned long last_updated; /* In jiffies */
  50
  51        u8 set_cnt; /* PWM (period) count number; 0xff stops fan */
  52        u8 act_cnt; /*   formula: cnt = (CLK * 30)/(rpm * P) */
  53        u8 fan_sta; /* bit 0: set when actual fan speed more than 20%
  54                     *   outside requested fan speed
  55                     * bit 1: set when fan speed below 1920 rpm
  56                     */
  57};
  58
  59#define G760A_DEFAULT_CLK 32768
  60#define G760A_DEFAULT_FAN_DIV 2
  61
  62#define PWM_FROM_CNT(cnt)       (0xff-(cnt))
  63#define PWM_TO_CNT(pwm)         (0xff-(pwm))
  64
  65static inline unsigned int rpm_from_cnt(u8 val, u32 clk, u16 div)
  66{
  67        return ((val == 0x00) ? 0 : ((clk*30)/(val*div)));
  68}
  69
  70/* read/write wrappers */
  71static int g760a_read_value(struct i2c_client *client, enum g760a_regs reg)
  72{
  73        return i2c_smbus_read_byte_data(client, reg);
  74}
  75
  76static int g760a_write_value(struct i2c_client *client, enum g760a_regs reg,
  77                             u16 value)
  78{
  79        return i2c_smbus_write_byte_data(client, reg, value);
  80}
  81
  82/*
  83 * sysfs attributes
  84 */
  85
  86static struct g760a_data *g760a_update_client(struct device *dev)
  87{
  88        struct g760a_data *data = dev_get_drvdata(dev);
  89        struct i2c_client *client = data->client;
  90
  91        mutex_lock(&data->update_lock);
  92
  93        if (time_after(jiffies, data->last_updated + G760A_UPDATE_INTERVAL)
  94            || !data->valid) {
  95                dev_dbg(&client->dev, "Starting g760a update\n");
  96
  97                data->set_cnt = g760a_read_value(client, G760A_REG_SET_CNT);
  98                data->act_cnt = g760a_read_value(client, G760A_REG_ACT_CNT);
  99                data->fan_sta = g760a_read_value(client, G760A_REG_FAN_STA);
 100
 101                data->last_updated = jiffies;
 102                data->valid = 1;
 103        }
 104
 105        mutex_unlock(&data->update_lock);
 106
 107        return data;
 108}
 109
 110static ssize_t fan1_input_show(struct device *dev,
 111                               struct device_attribute *da, char *buf)
 112{
 113        struct g760a_data *data = g760a_update_client(dev);
 114        unsigned int rpm = 0;
 115
 116        mutex_lock(&data->update_lock);
 117        if (!(data->fan_sta & G760A_REG_FAN_STA_RPM_LOW))
 118                rpm = rpm_from_cnt(data->act_cnt, data->clk, data->fan_div);
 119        mutex_unlock(&data->update_lock);
 120
 121        return sprintf(buf, "%d\n", rpm);
 122}
 123
 124static ssize_t fan1_alarm_show(struct device *dev,
 125                               struct device_attribute *da, char *buf)
 126{
 127        struct g760a_data *data = g760a_update_client(dev);
 128
 129        int fan_alarm = (data->fan_sta & G760A_REG_FAN_STA_RPM_OFF) ? 1 : 0;
 130
 131        return sprintf(buf, "%d\n", fan_alarm);
 132}
 133
 134static ssize_t pwm1_show(struct device *dev, struct device_attribute *da,
 135                         char *buf)
 136{
 137        struct g760a_data *data = g760a_update_client(dev);
 138
 139        return sprintf(buf, "%d\n", PWM_FROM_CNT(data->set_cnt));
 140}
 141
 142static ssize_t pwm1_store(struct device *dev, struct device_attribute *da,
 143                          const char *buf, size_t count)
 144{
 145        struct g760a_data *data = g760a_update_client(dev);
 146        struct i2c_client *client = data->client;
 147        unsigned long val;
 148
 149        if (kstrtoul(buf, 10, &val))
 150                return -EINVAL;
 151
 152        mutex_lock(&data->update_lock);
 153        data->set_cnt = PWM_TO_CNT(clamp_val(val, 0, 255));
 154        g760a_write_value(client, G760A_REG_SET_CNT, data->set_cnt);
 155        mutex_unlock(&data->update_lock);
 156
 157        return count;
 158}
 159
 160static DEVICE_ATTR_RW(pwm1);
 161static DEVICE_ATTR_RO(fan1_input);
 162static DEVICE_ATTR_RO(fan1_alarm);
 163
 164static struct attribute *g760a_attrs[] = {
 165        &dev_attr_pwm1.attr,
 166        &dev_attr_fan1_input.attr,
 167        &dev_attr_fan1_alarm.attr,
 168        NULL
 169};
 170
 171ATTRIBUTE_GROUPS(g760a);
 172
 173/*
 174 * new-style driver model code
 175 */
 176
 177static int g760a_probe(struct i2c_client *client,
 178                        const struct i2c_device_id *id)
 179{
 180        struct device *dev = &client->dev;
 181        struct g760a_data *data;
 182        struct device *hwmon_dev;
 183
 184        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 185                return -EIO;
 186
 187        data = devm_kzalloc(dev, sizeof(struct g760a_data), GFP_KERNEL);
 188        if (!data)
 189                return -ENOMEM;
 190
 191        data->client = client;
 192        mutex_init(&data->update_lock);
 193
 194        /* setup default configuration for now */
 195        data->fan_div = G760A_DEFAULT_FAN_DIV;
 196        data->clk = G760A_DEFAULT_CLK;
 197
 198        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 199                                                           data,
 200                                                           g760a_groups);
 201        return PTR_ERR_OR_ZERO(hwmon_dev);
 202}
 203
 204static const struct i2c_device_id g760a_id[] = {
 205        { "g760a", 0 },
 206        { }
 207};
 208MODULE_DEVICE_TABLE(i2c, g760a_id);
 209
 210static struct i2c_driver g760a_driver = {
 211        .driver = {
 212                .name   = "g760a",
 213        },
 214        .probe    = g760a_probe,
 215        .id_table = g760a_id,
 216};
 217
 218module_i2c_driver(g760a_driver);
 219
 220MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
 221MODULE_DESCRIPTION("GMT G760A driver");
 222MODULE_LICENSE("GPL");
 223