drivers/hwmon/ads7828.c

   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 /* Module parameters */
  51 static int se_input = 1; /* Default is SE, 0 == diff */
  52 static int int_vref = 1; /* Default is internal ref ON */
  53 static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
  54 module_param(se_input, bool, S_IRUGO);
  55 module_param(int_vref, bool, S_IRUGO);
  56 module_param(vref_mv, int, S_IRUGO);
  57
  58 /* Global Variables */
  59 static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
  60 static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
  61
  62 /* Each client has this additional data */
  63 struct ads7828_data {
  64         struct device *hwmon_dev;
  65         struct mutex update_lock; /* mutex protect updates */
  66         char valid; /* !=0 if following fields are valid */
  67         unsigned long last_updated; /* In jiffies */
  68         u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
  69 };
  70
  71 /* Function declaration - necessary due to function dependencies */
  72 static int ads7828_detect(struct i2c_client *client,
  73                           struct i2c_board_info *info);
  74 static int ads7828_probe(struct i2c_client *client,
  75                          const struct i2c_device_id *id);
  76
  77 /* The ADS7828 returns the 12-bit sample in two bytes,
  78         these are read as a word then byte-swapped */
  79 static u16 ads7828_read_value(struct i2c_client *client, u8 reg)
  80 {
  81         return swab16(i2c_smbus_read_word_data(client, reg));
  82 }
  83
  84 static inline u8 channel_cmd_byte(int ch)
  85 {
  86         /* cmd byte C2,C1,C0 - see datasheet */
  87         u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
  88         cmd |= ads7828_cmd_byte;
  89         return cmd;
  90 }
  91
  92 /* Update data for the device (all 8 channels) */
  93 static struct ads7828_data *ads7828_update_device(struct device *dev)
  94 {
  95         struct i2c_client *client = to_i2c_client(dev);
  96         struct ads7828_data *data = i2c_get_clientdata(client);
  97
  98         mutex_lock(&data->update_lock);
  99
 100         if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
 101                         || !data->valid) {
 102                 unsigned int ch;
 103                 dev_dbg(&client->dev, "Starting ads7828 update\n");
 104
 105                 for (ch = 0; ch < ADS7828_NCH; ch++) {
 106                         u8 cmd = channel_cmd_byte(ch);
 107                         data->adc_input[ch] = ads7828_read_value(client, cmd);
 108                 }
 109                 data->last_updated = jiffies;
 110                 data->valid = 1;
 111         }
 112
 113         mutex_unlock(&data->update_lock);
 114
 115         return data;
 116 }
 117
 118 /* sysfs callback function */
 119 static ssize_t show_in(struct device *dev, struct device_attribute *da,
 120         char *buf)
 121 {
 122         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 123         struct ads7828_data *data = ads7828_update_device(dev);
 124         /* Print value (in mV as specified in sysfs-interface documentation) */
 125         return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
 126                 ads7828_lsb_resol)/1000);
 127 }
 128
 129 #define in_reg(offset)\
 130 static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
 131         NULL, offset)
 132
 133 in_reg(0);
 134 in_reg(1);
 135 in_reg(2);
 136 in_reg(3);
 137 in_reg(4);
 138 in_reg(5);
 139 in_reg(6);
 140 in_reg(7);
 141
 142 static struct attribute *ads7828_attributes[] = {
 143         &sensor_dev_attr_in0_input.dev_attr.attr,
 144         &sensor_dev_attr_in1_input.dev_attr.attr,
 145         &sensor_dev_attr_in2_input.dev_attr.attr,
 146         &sensor_dev_attr_in3_input.dev_attr.attr,
 147         &sensor_dev_attr_in4_input.dev_attr.attr,
 148         &sensor_dev_attr_in5_input.dev_attr.attr,
 149         &sensor_dev_attr_in6_input.dev_attr.attr,
 150         &sensor_dev_attr_in7_input.dev_attr.attr,
 151         NULL
 152 };
 153
 154 static const struct attribute_group ads7828_group = {
 155         .attrs = ads7828_attributes,
 156 };
 157
 158 static int ads7828_remove(struct i2c_client *client)
 159 {
 160         struct ads7828_data *data = i2c_get_clientdata(client);
 161         hwmon_device_unregister(data->hwmon_dev);
 162         sysfs_remove_group(&client->dev.kobj, &ads7828_group);
 163         kfree(i2c_get_clientdata(client));
 164         return 0;
 165 }
 166
 167 static const struct i2c_device_id ads7828_id[] = {
 168         { "ads7828", 0 },
 169         { }
 170 };
 171 MODULE_DEVICE_TABLE(i2c, ads7828_id);
 172
 173 /* This is the driver that will be inserted */
 174 static struct i2c_driver ads7828_driver = {
 175         .class = I2C_CLASS_HWMON,
 176         .driver = {
 177                 .name = "ads7828",
 178         },
 179         .probe = ads7828_probe,
 180         .remove = ads7828_remove,
 181         .id_table = ads7828_id,
 182         .detect = ads7828_detect,
 183         .address_list = normal_i2c,
 184 };
 185
 186 /* Return 0 if detection is successful, -ENODEV otherwise */
 187 static int ads7828_detect(struct i2c_client *client,
 188                           struct i2c_board_info *info)
 189 {
 190         struct i2c_adapter *adapter = client->adapter;
 191         int ch;
 192
 193         /* Check we have a valid client */
 194         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
 195                 return -ENODEV;
 196
 197         /* Now, we do the remaining detection. There is no identification
 198         dedicated register so attempt to sanity check using knowledge of
 199         the chip
 200         - Read from the 8 channel addresses
 201         - Check the top 4 bits of each result are not set (12 data bits)
 202         */
 203         for (ch = 0; ch < ADS7828_NCH; ch++) {
 204                 u16 in_data;
 205                 u8 cmd = channel_cmd_byte(ch);
 206                 in_data = ads7828_read_value(client, cmd);
 207                 if (in_data & 0xF000) {
 208                         pr_debug("%s : Doesn't look like an ads7828 device\n",
 209                                  __func__);
 210                         return -ENODEV;
 211                 }
 212         }
 213
 214         strlcpy(info->type, "ads7828", I2C_NAME_SIZE);
 215
 216         return 0;
 217 }
 218
 219 static int ads7828_probe(struct i2c_client *client,
 220                          const struct i2c_device_id *id)
 221 {
 222         struct ads7828_data *data;
 223         int err;
 224
 225         data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
 226         if (!data) {
 227                 err = -ENOMEM;
 228                 goto exit;
 229         }
 230
 231         i2c_set_clientdata(client, data);
 232         mutex_init(&data->update_lock);
 233
 234         /* Register sysfs hooks */
 235         err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
 236         if (err)
 237                 goto exit_free;
 238
 239         data->hwmon_dev = hwmon_device_register(&client->dev);
 240         if (IS_ERR(data->hwmon_dev)) {
 241                 err = PTR_ERR(data->hwmon_dev);
 242                 goto exit_remove;
 243         }
 244
 245         return 0;
 246
 247 exit_remove:
 248         sysfs_remove_group(&client->dev.kobj, &ads7828_group);
 249 exit_free:
 250         kfree(data);
 251 exit:
 252         return err;
 253 }
 254
 255 static int __init sensors_ads7828_init(void)
 256 {
 257         /* Initialize the command byte according to module parameters */
 258         ads7828_cmd_byte = se_input ?
 259                 ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
 260         ads7828_cmd_byte |= int_vref ?
 261                 ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
 262
 263         /* Calculate the LSB resolution */
 264         ads7828_lsb_resol = (vref_mv*1000)/4096;
 265
 266         return i2c_add_driver(&ads7828_driver);
 267 }
 268
 269 static void __exit sensors_ads7828_exit(void)
 270 {
 271         i2c_del_driver(&ads7828_driver);
 272 }
 273
 274 MODULE_AUTHOR("Steve Hardy <steve@linuxrealtime.co.uk>");
 275 MODULE_DESCRIPTION("ADS7828 driver");
 276 MODULE_LICENSE("GPL");
 277
 278 module_init(sensors_ads7828_init);
 279 module_exit(sensors_ads7828_exit);