xref: /openbmc/linux/drivers/hwmon/ads7828.c (revision 22246614)
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 */
47 static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
48 	I2C_CLIENT_END };
49 
50 /* Insmod parameters */
51 I2C_CLIENT_INSMOD_1(ads7828);
52 
53 /* Other module parameters */
54 static int se_input = 1; /* Default is SE, 0 == diff */
55 static int int_vref = 1; /* Default is internal ref ON */
56 static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
57 module_param(se_input, bool, S_IRUGO);
58 module_param(int_vref, bool, S_IRUGO);
59 module_param(vref_mv, int, S_IRUGO);
60 
61 /* Global Variables */
62 static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
63 static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
64 
65 /* Each client has this additional data */
66 struct ads7828_data {
67 	struct i2c_client client;
68 	struct device *hwmon_dev;
69 	struct mutex update_lock; /* mutex protect updates */
70 	char valid; /* !=0 if following fields are valid */
71 	unsigned long last_updated; /* In jiffies */
72 	u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
73 };
74 
75 /* Function declaration - necessary due to function dependencies */
76 static int ads7828_detect(struct i2c_adapter *adapter, int address, int kind);
77 
78 /* The ADS7828 returns the 12-bit sample in two bytes,
79 	these are read as a word then byte-swapped */
80 static u16 ads7828_read_value(struct i2c_client *client, u8 reg)
81 {
82 	return swab16(i2c_smbus_read_word_data(client, reg));
83 }
84 
85 static inline u8 channel_cmd_byte(int ch)
86 {
87 	/* cmd byte C2,C1,C0 - see datasheet */
88 	u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
89 	cmd |= ads7828_cmd_byte;
90 	return cmd;
91 }
92 
93 /* Update data for the device (all 8 channels) */
94 static struct ads7828_data *ads7828_update_device(struct device *dev)
95 {
96 	struct i2c_client *client = to_i2c_client(dev);
97 	struct ads7828_data *data = i2c_get_clientdata(client);
98 
99 	mutex_lock(&data->update_lock);
100 
101 	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
102 			|| !data->valid) {
103 		unsigned int ch;
104 		dev_dbg(&client->dev, "Starting ads7828 update\n");
105 
106 		for (ch = 0; ch < ADS7828_NCH; ch++) {
107 			u8 cmd = channel_cmd_byte(ch);
108 			data->adc_input[ch] = ads7828_read_value(client, cmd);
109 		}
110 		data->last_updated = jiffies;
111 		data->valid = 1;
112 	}
113 
114 	mutex_unlock(&data->update_lock);
115 
116 	return data;
117 }
118 
119 /* sysfs callback function */
120 static ssize_t show_in(struct device *dev, struct device_attribute *da,
121 	char *buf)
122 {
123 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
124 	struct ads7828_data *data = ads7828_update_device(dev);
125 	/* Print value (in mV as specified in sysfs-interface documentation) */
126 	return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
127 		ads7828_lsb_resol)/1000);
128 }
129 
130 #define in_reg(offset)\
131 static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
132 	NULL, offset)
133 
134 in_reg(0);
135 in_reg(1);
136 in_reg(2);
137 in_reg(3);
138 in_reg(4);
139 in_reg(5);
140 in_reg(6);
141 in_reg(7);
142 
143 static struct attribute *ads7828_attributes[] = {
144 	&sensor_dev_attr_in0_input.dev_attr.attr,
145 	&sensor_dev_attr_in1_input.dev_attr.attr,
146 	&sensor_dev_attr_in2_input.dev_attr.attr,
147 	&sensor_dev_attr_in3_input.dev_attr.attr,
148 	&sensor_dev_attr_in4_input.dev_attr.attr,
149 	&sensor_dev_attr_in5_input.dev_attr.attr,
150 	&sensor_dev_attr_in6_input.dev_attr.attr,
151 	&sensor_dev_attr_in7_input.dev_attr.attr,
152 	NULL
153 };
154 
155 static const struct attribute_group ads7828_group = {
156 	.attrs = ads7828_attributes,
157 };
158 
159 static int ads7828_attach_adapter(struct i2c_adapter *adapter)
160 {
161 	if (!(adapter->class & I2C_CLASS_HWMON))
162 		return 0;
163 	return i2c_probe(adapter, &addr_data, ads7828_detect);
164 }
165 
166 static int ads7828_detach_client(struct i2c_client *client)
167 {
168 	struct ads7828_data *data = i2c_get_clientdata(client);
169 	hwmon_device_unregister(data->hwmon_dev);
170 	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
171 	i2c_detach_client(client);
172 	kfree(i2c_get_clientdata(client));
173 	return 0;
174 }
175 
176 /* This is the driver that will be inserted */
177 static struct i2c_driver ads7828_driver = {
178 	.driver = {
179 		.name = "ads7828",
180 	},
181 	.attach_adapter = ads7828_attach_adapter,
182 	.detach_client = ads7828_detach_client,
183 };
184 
185 /* This function is called by i2c_probe */
186 static int ads7828_detect(struct i2c_adapter *adapter, int address, int kind)
187 {
188 	struct i2c_client *client;
189 	struct ads7828_data *data;
190 	int err = 0;
191 	const char *name = "";
192 
193 	/* Check we have a valid client */
194 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
195 		goto exit;
196 
197 	/* OK. For now, we presume we have a valid client. We now create the
198 	client structure, even though we cannot fill it completely yet.
199 	But it allows us to access ads7828_read_value. */
200 	data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
201 	if (!data) {
202 		err = -ENOMEM;
203 		goto exit;
204 	}
205 
206 	client = &data->client;
207 	i2c_set_clientdata(client, data);
208 	client->addr = address;
209 	client->adapter = adapter;
210 	client->driver = &ads7828_driver;
211 
212 	/* Now, we do the remaining detection. There is no identification
213 	dedicated register so attempt to sanity check using knowledge of
214 	the chip
215 	- Read from the 8 channel addresses
216 	- Check the top 4 bits of each result are not set (12 data bits)
217 	*/
218 	if (kind < 0) {
219 		int ch;
220 		for (ch = 0; ch < ADS7828_NCH; ch++) {
221 			u16 in_data;
222 			u8 cmd = channel_cmd_byte(ch);
223 			in_data = ads7828_read_value(client, cmd);
224 			if (in_data & 0xF000) {
225 				printk(KERN_DEBUG
226 				"%s : Doesn't look like an ads7828 device\n",
227 				__func__);
228 				goto exit_free;
229 			}
230 		}
231 	}
232 
233 	/* Determine the chip type - only one kind supported! */
234 	if (kind <= 0)
235 		kind = ads7828;
236 
237 	if (kind == ads7828)
238 		name = "ads7828";
239 
240 	/* Fill in the remaining client fields, put it into the global list */
241 	strlcpy(client->name, name, I2C_NAME_SIZE);
242 
243 	mutex_init(&data->update_lock);
244 
245 	/* Tell the I2C layer a new client has arrived */
246 	err = i2c_attach_client(client);
247 	if (err)
248 		goto exit_free;
249 
250 	/* Register sysfs hooks */
251 	err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
252 	if (err)
253 		goto exit_detach;
254 
255 	data->hwmon_dev = hwmon_device_register(&client->dev);
256 	if (IS_ERR(data->hwmon_dev)) {
257 		err = PTR_ERR(data->hwmon_dev);
258 		goto exit_remove;
259 	}
260 
261 	return 0;
262 
263 exit_remove:
264 	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
265 exit_detach:
266 	i2c_detach_client(client);
267 exit_free:
268 	kfree(data);
269 exit:
270 	return err;
271 }
272 
273 static int __init sensors_ads7828_init(void)
274 {
275 	/* Initialize the command byte according to module parameters */
276 	ads7828_cmd_byte = se_input ?
277 		ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
278 	ads7828_cmd_byte |= int_vref ?
279 		ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
280 
281 	/* Calculate the LSB resolution */
282 	ads7828_lsb_resol = (vref_mv*1000)/4096;
283 
284 	return i2c_add_driver(&ads7828_driver);
285 }
286 
287 static void __exit sensors_ads7828_exit(void)
288 {
289 	i2c_del_driver(&ads7828_driver);
290 }
291 
292 MODULE_AUTHOR("Steve Hardy <steve@linuxrealtime.co.uk>");
293 MODULE_DESCRIPTION("ADS7828 driver");
294 MODULE_LICENSE("GPL");
295 
296 module_init(sensors_ads7828_init);
297 module_exit(sensors_ads7828_exit);
298