drivers/hwmon/ads7871.c

   1 /*
   2  *  ads7871 - driver for TI ADS7871 A/D converter
   3  *
   4  *  Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
   5  *
   6  *  This program is distributed in the hope that it will be useful,
   7  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   8  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   9  *  GNU General Public License for more details.
  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 version 2 or
  13  *  later as publishhed by the Free Software Foundation.
  14  *
  15  *      You need to have something like this in struct spi_board_info
  16  *      {
  17  *              .modalias       = "ads7871",
  18  *              .max_speed_hz   = 2*1000*1000,
  19  *              .chip_select    = 0,
  20  *              .bus_num        = 1,
  21  *      },
  22  */
  23
  24 /*From figure 18 in the datasheet*/
  25 /*Register addresses*/
  26 #define REG_LS_BYTE     0 /*A/D Output Data, LS Byte*/
  27 #define REG_MS_BYTE     1 /*A/D Output Data, MS Byte*/
  28 #define REG_PGA_VALID   2 /*PGA Valid Register*/
  29 #define REG_AD_CONTROL  3 /*A/D Control Register*/
  30 #define REG_GAIN_MUX    4 /*Gain/Mux Register*/
  31 #define REG_IO_STATE    5 /*Digital I/O State Register*/
  32 #define REG_IO_CONTROL  6 /*Digital I/O Control Register*/
  33 #define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
  34 #define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
  35 #define REG_ID          31 /*ID Register*/
  36
  37 /*
  38  * From figure 17 in the datasheet
  39  * These bits get ORed with the address to form
  40  * the instruction byte
  41  */
  42 /*Instruction Bit masks*/
  43 #define INST_MODE_bm    (1<<7)
  44 #define INST_READ_bm    (1<<6)
  45 #define INST_16BIT_bm   (1<<5)
  46
  47 /*From figure 18 in the datasheet*/
  48 /*bit masks for Rev/Oscillator Control Register*/
  49 #define MUX_CNV_bv      7
  50 #define MUX_CNV_bm      (1<<MUX_CNV_bv)
  51 #define MUX_M3_bm       (1<<3) /*M3 selects single ended*/
  52 #define MUX_G_bv        4 /*allows for reg = (gain << MUX_G_bv) | ...*/
  53
  54 /*From figure 18 in the datasheet*/
  55 /*bit masks for Rev/Oscillator Control Register*/
  56 #define OSC_OSCR_bm     (1<<5)
  57 #define OSC_OSCE_bm     (1<<4)
  58 #define OSC_REFE_bm     (1<<3)
  59 #define OSC_BUFE_bm     (1<<2)
  60 #define OSC_R2V_bm      (1<<1)
  61 #define OSC_RBG_bm      (1<<0)
  62
  63 #include <linux/module.h>
  64 #include <linux/init.h>
  65 #include <linux/spi/spi.h>
  66 #include <linux/hwmon.h>
  67 #include <linux/hwmon-sysfs.h>
  68 #include <linux/err.h>
  69 #include <linux/mutex.h>
  70 #include <linux/delay.h>
  71
  72 #define DEVICE_NAME     "ads7871"
  73
  74 struct ads7871_data {
  75         struct device   *hwmon_dev;
  76         struct mutex    update_lock;
  77 };
  78
  79 static int ads7871_read_reg8(struct spi_device *spi, int reg)
  80 {
  81         int ret;
  82         reg = reg | INST_READ_bm;
  83         ret = spi_w8r8(spi, reg);
  84         return ret;
  85 }
  86
  87 static int ads7871_read_reg16(struct spi_device *spi, int reg)
  88 {
  89         int ret;
  90         reg = reg | INST_READ_bm | INST_16BIT_bm;
  91         ret = spi_w8r16(spi, reg);
  92         return ret;
  93 }
  94
  95 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
  96 {
  97         u8 tmp[2] = {reg, val};
  98         return spi_write(spi, tmp, sizeof(tmp));
  99 }
 100
 101 static ssize_t show_voltage(struct device *dev,
 102                 struct device_attribute *da, char *buf)
 103 {
 104         struct spi_device *spi = to_spi_device(dev);
 105         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 106         int ret, val, i = 0;
 107         uint8_t channel, mux_cnv;
 108
 109         channel = attr->index;
 110         /*
 111          * TODO: add support for conversions
 112          * other than single ended with a gain of 1
 113          */
 114         /*MUX_M3_bm forces single ended*/
 115         /*This is also where the gain of the PGA would be set*/
 116         ads7871_write_reg8(spi, REG_GAIN_MUX,
 117                 (MUX_CNV_bm | MUX_M3_bm | channel));
 118
 119         ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 120         mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
 121         /*
 122          * on 400MHz arm9 platform the conversion
 123          * is already done when we do this test
 124          */
 125         while ((i < 2) && mux_cnv) {
 126                 i++;
 127                 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 128                 mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
 129                 msleep_interruptible(1);
 130         }
 131
 132         if (mux_cnv == 0) {
 133                 val = ads7871_read_reg16(spi, REG_LS_BYTE);
 134                 /*result in volts*10000 = (val/8192)*2.5*10000*/
 135                 val = ((val>>2) * 25000) / 8192;
 136                 return sprintf(buf, "%d\n", val);
 137         } else {
 138                 return -1;
 139         }
 140 }
 141
 142 static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
 143 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
 144 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
 145 static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
 146 static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
 147 static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
 148 static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
 149 static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
 150
 151 static struct attribute *ads7871_attributes[] = {
 152         &sensor_dev_attr_in0_input.dev_attr.attr,
 153         &sensor_dev_attr_in1_input.dev_attr.attr,
 154         &sensor_dev_attr_in2_input.dev_attr.attr,
 155         &sensor_dev_attr_in3_input.dev_attr.attr,
 156         &sensor_dev_attr_in4_input.dev_attr.attr,
 157         &sensor_dev_attr_in5_input.dev_attr.attr,
 158         &sensor_dev_attr_in6_input.dev_attr.attr,
 159         &sensor_dev_attr_in7_input.dev_attr.attr,
 160         NULL
 161 };
 162
 163 static const struct attribute_group ads7871_group = {
 164         .attrs = ads7871_attributes,
 165 };
 166
 167 static int __devinit ads7871_probe(struct spi_device *spi)
 168 {
 169         int ret, err;
 170         uint8_t val;
 171         struct ads7871_data *pdata;
 172
 173         dev_dbg(&spi->dev, "probe\n");
 174
 175         /* Configure the SPI bus */
 176         spi->mode = (SPI_MODE_0);
 177         spi->bits_per_word = 8;
 178         spi_setup(spi);
 179
 180         ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
 181         ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
 182
 183         val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm);
 184         ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
 185         ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
 186
 187         dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
 188         /*
 189          * because there is no other error checking on an SPI bus
 190          * we need to make sure we really have a chip
 191          */
 192         if (val != ret) {
 193                 err = -ENODEV;
 194                 goto exit;
 195         }
 196
 197         pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL);
 198         if (!pdata) {
 199                 err = -ENOMEM;
 200                 goto exit;
 201         }
 202
 203         err = sysfs_create_group(&spi->dev.kobj, &ads7871_group);
 204         if (err < 0)
 205                 goto error_free;
 206
 207         spi_set_drvdata(spi, pdata);
 208
 209         pdata->hwmon_dev = hwmon_device_register(&spi->dev);
 210         if (IS_ERR(pdata->hwmon_dev)) {
 211                 err = PTR_ERR(pdata->hwmon_dev);
 212                 goto error_remove;
 213         }
 214
 215         return 0;
 216
 217 error_remove:
 218         sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
 219 error_free:
 220         kfree(pdata);
 221 exit:
 222         return err;
 223 }
 224
 225 static int __devexit ads7871_remove(struct spi_device *spi)
 226 {
 227         struct ads7871_data *pdata = spi_get_drvdata(spi);
 228
 229         hwmon_device_unregister(pdata->hwmon_dev);
 230         sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
 231         kfree(pdata);
 232         return 0;
 233 }
 234
 235 static struct spi_driver ads7871_driver = {
 236         .driver = {
 237                 .name = DEVICE_NAME,
 238                 .owner = THIS_MODULE,
 239         },
 240
 241         .probe = ads7871_probe,
 242         .remove = __devexit_p(ads7871_remove),
 243 };
 244
 245 module_spi_driver(ads7871_driver);
 246
 247 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 248 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 249 MODULE_LICENSE("GPL");