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/delay.h>
  70
  71 #define DEVICE_NAME     "ads7871"
  72
  73 struct ads7871_data {
  74         struct spi_device *spi;
  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 ads7871_data *pdata = dev_get_drvdata(dev);
 103         struct spi_device *spi = pdata->spi;
 104         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 105         int ret, val, i = 0;
 106         uint8_t channel, mux_cnv;
 107
 108         channel = attr->index;
 109         /*
 110          * TODO: add support for conversions
 111          * other than single ended with a gain of 1
 112          */
 113         /*MUX_M3_BM forces single ended*/
 114         /*This is also where the gain of the PGA would be set*/
 115         ads7871_write_reg8(spi, REG_GAIN_MUX,
 116                 (MUX_CNV_BM | MUX_M3_BM | channel));
 117
 118         ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 119         mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
 120         /*
 121          * on 400MHz arm9 platform the conversion
 122          * is already done when we do this test
 123          */
 124         while ((i < 2) && mux_cnv) {
 125                 i++;
 126                 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 127                 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
 128                 msleep_interruptible(1);
 129         }
 130
 131         if (mux_cnv == 0) {
 132                 val = ads7871_read_reg16(spi, REG_LS_BYTE);
 133                 /*result in volts*10000 = (val/8192)*2.5*10000*/
 134                 val = ((val >> 2) * 25000) / 8192;
 135                 return sprintf(buf, "%d\n", val);
 136         } else {
 137                 return -1;
 138         }
 139 }
 140
 141 static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
 142 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
 143 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
 144 static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
 145 static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
 146 static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
 147 static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
 148 static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
 149
 150 static struct attribute *ads7871_attrs[] = {
 151         &sensor_dev_attr_in0_input.dev_attr.attr,
 152         &sensor_dev_attr_in1_input.dev_attr.attr,
 153         &sensor_dev_attr_in2_input.dev_attr.attr,
 154         &sensor_dev_attr_in3_input.dev_attr.attr,
 155         &sensor_dev_attr_in4_input.dev_attr.attr,
 156         &sensor_dev_attr_in5_input.dev_attr.attr,
 157         &sensor_dev_attr_in6_input.dev_attr.attr,
 158         &sensor_dev_attr_in7_input.dev_attr.attr,
 159         NULL
 160 };
 161
 162 ATTRIBUTE_GROUPS(ads7871);
 163
 164 static int ads7871_probe(struct spi_device *spi)
 165 {
 166         struct device *dev = &spi->dev;
 167         int ret;
 168         uint8_t val;
 169         struct ads7871_data *pdata;
 170         struct device *hwmon_dev;
 171
 172         /* Configure the SPI bus */
 173         spi->mode = (SPI_MODE_0);
 174         spi->bits_per_word = 8;
 175         spi_setup(spi);
 176
 177         ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
 178         ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
 179
 180         val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
 181         ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
 182         ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
 183
 184         dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
 185         /*
 186          * because there is no other error checking on an SPI bus
 187          * we need to make sure we really have a chip
 188          */
 189         if (val != ret)
 190                 return -ENODEV;
 191
 192         pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
 193         if (!pdata)
 194                 return -ENOMEM;
 195
 196         pdata->spi = spi;
 197
 198         hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
 199                                                            pdata,
 200                                                            ads7871_groups);
 201         return PTR_ERR_OR_ZERO(hwmon_dev);
 202 }
 203
 204 static struct spi_driver ads7871_driver = {
 205         .driver = {
 206                 .name = DEVICE_NAME,
 207         },
 208         .probe = ads7871_probe,
 209 };
 210
 211 module_spi_driver(ads7871_driver);
 212
 213 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 214 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 215 MODULE_LICENSE("GPL");