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 show_fan(struct device *dev, struct device_attribute *da,
111			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 show_fan_alarm(struct device *dev, struct device_attribute *da,
125			      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 get_pwm(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 set_pwm(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(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
161static DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL);
162static DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL);
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