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 /*From figure 17 in the datasheet
  38 * These bits get ORed with the address to form
  39 * the instruction byte */
  40 /*Instruction Bit masks*/
  41 #define INST_MODE_bm    (1<<7)
  42 #define INST_READ_bm    (1<<6)
  43 #define INST_16BIT_bm   (1<<5)
  44
  45 /*From figure 18 in the datasheet*/
  46 /*bit masks for Rev/Oscillator Control Register*/
  47 #define MUX_CNV_bv      7
  48 #define MUX_CNV_bm      (1<<MUX_CNV_bv)
  49 #define MUX_M3_bm       (1<<3) /*M3 selects single ended*/
  50 #define MUX_G_bv        4 /*allows for reg = (gain << MUX_G_bv) | ...*/
  51
  52 /*From figure 18 in the datasheet*/
  53 /*bit masks for Rev/Oscillator Control Register*/
  54 #define OSC_OSCR_bm     (1<<5)
  55 #define OSC_OSCE_bm     (1<<4)
  56 #define OSC_REFE_bm     (1<<3)
  57 #define OSC_BUFE_bm     (1<<2)
  58 #define OSC_R2V_bm      (1<<1)
  59 #define OSC_RBG_bm      (1<<0)
  60
  61 #include <linux/module.h>
  62 #include <linux/init.h>
  63 #include <linux/spi/spi.h>
  64 #include <linux/hwmon.h>
  65 #include <linux/hwmon-sysfs.h>
  66 #include <linux/err.h>
  67 #include <linux/mutex.h>
  68 #include <linux/delay.h>
  69
  70 #define DEVICE_NAME     "ads7871"
  71
  72 struct ads7871_data {
  73         struct device   *hwmon_dev;
  74         struct mutex    update_lock;
  75 };
  76
  77 static int ads7871_read_reg8(struct spi_device *spi, int reg)
  78 {
  79         int ret;
  80         reg = reg | INST_READ_bm;
  81         ret = spi_w8r8(spi, reg);
  82         return ret;
  83 }
  84
  85 static int ads7871_read_reg16(struct spi_device *spi, int reg)
  86 {
  87         int ret;
  88         reg = reg | INST_READ_bm | INST_16BIT_bm;
  89         ret = spi_w8r16(spi, reg);
  90         return ret;
  91 }
  92
  93 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
  94 {
  95         u8 tmp[2] = {reg, val};
  96         return spi_write(spi, tmp, sizeof(tmp));
  97 }
  98
  99 static ssize_t show_voltage(struct device *dev,
 100                 struct device_attribute *da, char *buf)
 101 {
 102         struct spi_device *spi = to_spi_device(dev);
 103         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 104         int ret, val, i = 0;
 105         uint8_t channel, mux_cnv;
 106
 107         channel = attr->index;
 108         /*TODO: add support for conversions
 109          *other than single ended with a gain of 1*/
 110         /*MUX_M3_bm forces single ended*/
 111         /*This is also where the gain of the PGA would be set*/
 112         ads7871_write_reg8(spi, REG_GAIN_MUX,
 113                 (MUX_CNV_bm | MUX_M3_bm | channel));
 114
 115         ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 116         mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
 117         /*on 400MHz arm9 platform the conversion
 118          *is already done when we do this test*/
 119         while ((i < 2) && mux_cnv) {
 120                 i++;
 121                 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 122                 mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
 123                 msleep_interruptible(1);
 124         }
 125
 126         if (mux_cnv == 0) {
 127                 val = ads7871_read_reg16(spi, REG_LS_BYTE);
 128                 /*result in volts*10000 = (val/8192)*2.5*10000*/
 129                 val = ((val>>2) * 25000) / 8192;
 130                 return sprintf(buf, "%d\n", val);
 131         } else {
 132                 return -1;
 133         }
 134 }
 135
 136 static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
 137 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
 138 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
 139 static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
 140 static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
 141 static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
 142 static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
 143 static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
 144
 145 static struct attribute *ads7871_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
 157 static const struct attribute_group ads7871_group = {
 158         .attrs = ads7871_attributes,
 159 };
 160
 161 static int __devinit ads7871_probe(struct spi_device *spi)
 162 {
 163         int status, ret, err = 0;
 164         uint8_t val;
 165         struct ads7871_data *pdata;
 166
 167         dev_dbg(&spi->dev, "probe\n");
 168
 169         pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL);
 170         if (!pdata) {
 171                 err = -ENOMEM;
 172                 goto exit;
 173         }
 174
 175         status = sysfs_create_group(&spi->dev.kobj, &ads7871_group);
 176         if (status < 0)
 177                 goto error_free;
 178
 179         pdata->hwmon_dev = hwmon_device_register(&spi->dev);
 180         if (IS_ERR(pdata->hwmon_dev)) {
 181                 err = PTR_ERR(pdata->hwmon_dev);
 182                 goto error_remove;
 183         }
 184
 185         spi_set_drvdata(spi, pdata);
 186
 187         /* Configure the SPI bus */
 188         spi->mode = (SPI_MODE_0);
 189         spi->bits_per_word = 8;
 190         spi_setup(spi);
 191
 192         ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
 193         ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
 194
 195         val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm);
 196         ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
 197         ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
 198
 199         dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
 200         /*because there is no other error checking on an SPI bus
 201         we need to make sure we really have a chip*/
 202         if (val != ret) {
 203                 err = -ENODEV;
 204                 goto error_remove;
 205         }
 206
 207         return 0;
 208
 209 error_remove:
 210         sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
 211 error_free:
 212         kfree(pdata);
 213 exit:
 214         return err;
 215 }
 216
 217 static int __devexit ads7871_remove(struct spi_device *spi)
 218 {
 219         struct ads7871_data *pdata = spi_get_drvdata(spi);
 220
 221         hwmon_device_unregister(pdata->hwmon_dev);
 222         sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
 223         kfree(pdata);
 224         return 0;
 225 }
 226
 227 static struct spi_driver ads7871_driver = {
 228         .driver = {
 229                 .name = DEVICE_NAME,
 230                 .bus = &spi_bus_type,
 231                 .owner = THIS_MODULE,
 232         },
 233
 234         .probe = ads7871_probe,
 235         .remove = __devexit_p(ads7871_remove),
 236 };
 237
 238 static int __init ads7871_init(void)
 239 {
 240         return spi_register_driver(&ads7871_driver);
 241 }
 242
 243 static void __exit ads7871_exit(void)
 244 {
 245         spi_unregister_driver(&ads7871_driver);
 246 }
 247
 248 module_init(ads7871_init);
 249 module_exit(ads7871_exit);
 250
 251 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 252 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 253 MODULE_LICENSE("GPL");