ads7828.c revision c3813d6af177fab19e322f3114b1f64fbcf08d71 
1/*
2	ads7828.c - lm_sensors driver for ads7828 12-bit 8-channel ADC
3	(C) 2007 EADS Astrium
4
5	This driver is based on the lm75 and other lm_sensors/hwmon drivers
6
7	Written by Steve Hardy <steve@linuxrealtime.co.uk>
8
9	Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
10
11	This program is free software; you can redistribute it and/or modify
12	it under the terms of the GNU General Public License as published by
13	the Free Software Foundation; either version 2 of the License, or
14	(at your option) any later version.
15
16	This program is distributed in the hope that it will be useful,
17	but WITHOUT ANY WARRANTY; without even the implied warranty of
18	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
19	GNU General Public License for more details.
20
21	You should have received a copy of the GNU General Public License
22	along with this program; if not, write to the Free Software
23	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24*/
25
26#include <linux/module.h>
27#include <linux/init.h>
28#include <linux/slab.h>
29#include <linux/jiffies.h>
30#include <linux/i2c.h>
31#include <linux/hwmon.h>
32#include <linux/hwmon-sysfs.h>
33#include <linux/err.h>
34#include <linux/mutex.h>
35
36/* The ADS7828 registers */
37#define ADS7828_NCH 8 /* 8 channels of 12-bit A-D supported */
38#define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
39#define ADS7828_CMD_SD_DIFF 0x00 /* Differential inputs */
40#define ADS7828_CMD_PD0 0x0 /* Power Down between A-D conversions */
41#define ADS7828_CMD_PD1 0x04 /* Internal ref OFF && A-D ON */
42#define ADS7828_CMD_PD2 0x08 /* Internal ref ON && A-D OFF */
43#define ADS7828_CMD_PD3 0x0C /* Internal ref ON && A-D ON */
44#define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
45
46/* Addresses to scan */
47static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
48	I2C_CLIENT_END };
49
50/* Insmod parameters */
51I2C_CLIENT_INSMOD_1(ads7828);
52
53/* Other module parameters */
54static int se_input = 1; /* Default is SE, 0 == diff */
55static int int_vref = 1; /* Default is internal ref ON */
56static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
57module_param(se_input, bool, S_IRUGO);
58module_param(int_vref, bool, S_IRUGO);
59module_param(vref_mv, int, S_IRUGO);
60
61/* Global Variables */
62static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
63static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
64
65/* Each client has this additional data */
66struct ads7828_data {
67	struct device *hwmon_dev;
68	struct mutex update_lock; /* mutex protect updates */
69	char valid; /* !=0 if following fields are valid */
70	unsigned long last_updated; /* In jiffies */
71	u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
72};
73
74/* Function declaration - necessary due to function dependencies */
75static int ads7828_detect(struct i2c_client *client,
76			  struct i2c_board_info *info);
77static int ads7828_probe(struct i2c_client *client,
78			 const struct i2c_device_id *id);
79
80/* The ADS7828 returns the 12-bit sample in two bytes,
81	these are read as a word then byte-swapped */
82static u16 ads7828_read_value(struct i2c_client *client, u8 reg)
83{
84	return swab16(i2c_smbus_read_word_data(client, reg));
85}
86
87static inline u8 channel_cmd_byte(int ch)
88{
89	/* cmd byte C2,C1,C0 - see datasheet */
90	u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
91	cmd |= ads7828_cmd_byte;
92	return cmd;
93}
94
95/* Update data for the device (all 8 channels) */
96static struct ads7828_data *ads7828_update_device(struct device *dev)
97{
98	struct i2c_client *client = to_i2c_client(dev);
99	struct ads7828_data *data = i2c_get_clientdata(client);
100
101	mutex_lock(&data->update_lock);
102
103	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
104			|| !data->valid) {
105		unsigned int ch;
106		dev_dbg(&client->dev, "Starting ads7828 update\n");
107
108		for (ch = 0; ch < ADS7828_NCH; ch++) {
109			u8 cmd = channel_cmd_byte(ch);
110			data->adc_input[ch] = ads7828_read_value(client, cmd);
111		}
112		data->last_updated = jiffies;
113		data->valid = 1;
114	}
115
116	mutex_unlock(&data->update_lock);
117
118	return data;
119}
120
121/* sysfs callback function */
122static ssize_t show_in(struct device *dev, struct device_attribute *da,
123	char *buf)
124{
125	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
126	struct ads7828_data *data = ads7828_update_device(dev);
127	/* Print value (in mV as specified in sysfs-interface documentation) */
128	return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
129		ads7828_lsb_resol)/1000);
130}
131
132#define in_reg(offset)\
133static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
134	NULL, offset)
135
136in_reg(0);
137in_reg(1);
138in_reg(2);
139in_reg(3);
140in_reg(4);
141in_reg(5);
142in_reg(6);
143in_reg(7);
144
145static struct attribute *ads7828_attributes[] = {
146	&sensor_dev_attr_in0_input.dev_attr.attr,
147	&sensor_dev_attr_in1_input.dev_attr.attr,
148	&sensor_dev_attr_in2_input.dev_attr.attr,
149	&sensor_dev_attr_in3_input.dev_attr.attr,
150	&sensor_dev_attr_in4_input.dev_attr.attr,
151	&sensor_dev_attr_in5_input.dev_attr.attr,
152	&sensor_dev_attr_in6_input.dev_attr.attr,
153	&sensor_dev_attr_in7_input.dev_attr.attr,
154	NULL
155};
156
157static const struct attribute_group ads7828_group = {
158	.attrs = ads7828_attributes,
159};
160
161static int ads7828_remove(struct i2c_client *client)
162{
163	struct ads7828_data *data = i2c_get_clientdata(client);
164	hwmon_device_unregister(data->hwmon_dev);
165	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
166	kfree(i2c_get_clientdata(client));
167	return 0;
168}
169
170static const struct i2c_device_id ads7828_id[] = {
171	{ "ads7828", ads7828 },
172	{ }
173};
174MODULE_DEVICE_TABLE(i2c, ads7828_id);
175
176/* This is the driver that will be inserted */
177static struct i2c_driver ads7828_driver = {
178	.class = I2C_CLASS_HWMON,
179	.driver = {
180		.name = "ads7828",
181	},
182	.probe = ads7828_probe,
183	.remove = ads7828_remove,
184	.id_table = ads7828_id,
185	.detect = ads7828_detect,
186	.address_list = normal_i2c,
187};
188
189/* Return 0 if detection is successful, -ENODEV otherwise */
190static int ads7828_detect(struct i2c_client *client,
191			  struct i2c_board_info *info)
192{
193	struct i2c_adapter *adapter = client->adapter;
194	int ch;
195
196	/* Check we have a valid client */
197	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
198		return -ENODEV;
199
200	/* Now, we do the remaining detection. There is no identification
201	dedicated register so attempt to sanity check using knowledge of
202	the chip
203	- Read from the 8 channel addresses
204	- Check the top 4 bits of each result are not set (12 data bits)
205	*/
206	for (ch = 0; ch < ADS7828_NCH; ch++) {
207		u16 in_data;
208		u8 cmd = channel_cmd_byte(ch);
209		in_data = ads7828_read_value(client, cmd);
210		if (in_data & 0xF000) {
211			pr_debug("%s : Doesn't look like an ads7828 device\n",
212				 __func__);
213			return -ENODEV;
214		}
215	}
216
217	strlcpy(info->type, "ads7828", I2C_NAME_SIZE);
218
219	return 0;
220}
221
222static int ads7828_probe(struct i2c_client *client,
223			 const struct i2c_device_id *id)
224{
225	struct ads7828_data *data;
226	int err;
227
228	data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
229	if (!data) {
230		err = -ENOMEM;
231		goto exit;
232	}
233
234	i2c_set_clientdata(client, data);
235	mutex_init(&data->update_lock);
236
237	/* Register sysfs hooks */
238	err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
239	if (err)
240		goto exit_free;
241
242	data->hwmon_dev = hwmon_device_register(&client->dev);
243	if (IS_ERR(data->hwmon_dev)) {
244		err = PTR_ERR(data->hwmon_dev);
245		goto exit_remove;
246	}
247
248	return 0;
249
250exit_remove:
251	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
252exit_free:
253	kfree(data);
254exit:
255	return err;
256}
257
258static int __init sensors_ads7828_init(void)
259{
260	/* Initialize the command byte according to module parameters */
261	ads7828_cmd_byte = se_input ?
262		ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
263	ads7828_cmd_byte |= int_vref ?
264		ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
265
266	/* Calculate the LSB resolution */
267	ads7828_lsb_resol = (vref_mv*1000)/4096;
268
269	return i2c_add_driver(&ads7828_driver);
270}
271
272static void __exit sensors_ads7828_exit(void)
273{
274	i2c_del_driver(&ads7828_driver);
275}
276
277MODULE_AUTHOR("Steve Hardy <steve@linuxrealtime.co.uk>");
278MODULE_DESCRIPTION("ADS7828 driver");
279MODULE_LICENSE("GPL");
280
281module_init(sensors_ads7828_init);
282module_exit(sensors_ads7828_exit);
283