root/drivers/hwmon/ads7871.c

DEFINITIONS

1. ads7871_read_reg8
2. ads7871_read_reg16
3. ads7871_write_reg8
4. voltage_show
5. ads7871_probe

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  ads7871 - driver for TI ADS7871 A/D converter
   4  *
   5  *  Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
   6  *
   7  *      You need to have something like this in struct spi_board_info
   8  *      {
   9  *              .modalias       = "ads7871",
  10  *              .max_speed_hz   = 2*1000*1000,
  11  *              .chip_select    = 0,
  12  *              .bus_num        = 1,
  13  *      },
  14  */
  15 
  16 /*From figure 18 in the datasheet*/
  17 /*Register addresses*/
  18 #define REG_LS_BYTE     0 /*A/D Output Data, LS Byte*/
  19 #define REG_MS_BYTE     1 /*A/D Output Data, MS Byte*/
  20 #define REG_PGA_VALID   2 /*PGA Valid Register*/
  21 #define REG_AD_CONTROL  3 /*A/D Control Register*/
  22 #define REG_GAIN_MUX    4 /*Gain/Mux Register*/
  23 #define REG_IO_STATE    5 /*Digital I/O State Register*/
  24 #define REG_IO_CONTROL  6 /*Digital I/O Control Register*/
  25 #define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
  26 #define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
  27 #define REG_ID          31 /*ID Register*/
  28 
  29 /*
  30  * From figure 17 in the datasheet
  31  * These bits get ORed with the address to form
  32  * the instruction byte
  33  */
  34 /*Instruction Bit masks*/
  35 #define INST_MODE_BM    (1 << 7)
  36 #define INST_READ_BM    (1 << 6)
  37 #define INST_16BIT_BM   (1 << 5)
  38 
  39 /*From figure 18 in the datasheet*/
  40 /*bit masks for Rev/Oscillator Control Register*/
  41 #define MUX_CNV_BV      7
  42 #define MUX_CNV_BM      (1 << MUX_CNV_BV)
  43 #define MUX_M3_BM       (1 << 3) /*M3 selects single ended*/
  44 #define MUX_G_BV        4 /*allows for reg = (gain << MUX_G_BV) | ...*/
  45 
  46 /*From figure 18 in the datasheet*/
  47 /*bit masks for Rev/Oscillator Control Register*/
  48 #define OSC_OSCR_BM     (1 << 5)
  49 #define OSC_OSCE_BM     (1 << 4)
  50 #define OSC_REFE_BM     (1 << 3)
  51 #define OSC_BUFE_BM     (1 << 2)
  52 #define OSC_R2V_BM      (1 << 1)
  53 #define OSC_RBG_BM      (1 << 0)
  54 
  55 #include <linux/module.h>
  56 #include <linux/init.h>
  57 #include <linux/spi/spi.h>
  58 #include <linux/hwmon.h>
  59 #include <linux/hwmon-sysfs.h>
  60 #include <linux/err.h>
  61 #include <linux/delay.h>
  62 
  63 #define DEVICE_NAME     "ads7871"
  64 
  65 struct ads7871_data {
  66         struct spi_device *spi;
  67 };
  68 
  69 static int ads7871_read_reg8(struct spi_device *spi, int reg)
  70 {
  71         int ret;
  72         reg = reg | INST_READ_BM;
  73         ret = spi_w8r8(spi, reg);
  74         return ret;
  75 }
  76 
  77 static int ads7871_read_reg16(struct spi_device *spi, int reg)
  78 {
  79         int ret;
  80         reg = reg | INST_READ_BM | INST_16BIT_BM;
  81         ret = spi_w8r16(spi, reg);
  82         return ret;
  83 }
  84 
  85 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
  86 {
  87         u8 tmp[2] = {reg, val};
  88         return spi_write(spi, tmp, sizeof(tmp));
  89 }
  90 
  91 static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
  92                             char *buf)
  93 {
  94         struct ads7871_data *pdata = dev_get_drvdata(dev);
  95         struct spi_device *spi = pdata->spi;
  96         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  97         int ret, val, i = 0;
  98         uint8_t channel, mux_cnv;
  99 
 100         channel = attr->index;
 101         /*
 102          * TODO: add support for conversions
 103          * other than single ended with a gain of 1
 104          */
 105         /*MUX_M3_BM forces single ended*/
 106         /*This is also where the gain of the PGA would be set*/
 107         ads7871_write_reg8(spi, REG_GAIN_MUX,
 108                 (MUX_CNV_BM | MUX_M3_BM | channel));
 109 
 110         ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 111         mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
 112         /*
 113          * on 400MHz arm9 platform the conversion
 114          * is already done when we do this test
 115          */
 116         while ((i < 2) && mux_cnv) {
 117                 i++;
 118                 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
 119                 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
 120                 msleep_interruptible(1);
 121         }
 122 
 123         if (mux_cnv == 0) {
 124                 val = ads7871_read_reg16(spi, REG_LS_BYTE);
 125                 /*result in volts*10000 = (val/8192)*2.5*10000*/
 126                 val = ((val >> 2) * 25000) / 8192;
 127                 return sprintf(buf, "%d\n", val);
 128         } else {
 129                 return -1;
 130         }
 131 }
 132 
 133 static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
 134 static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
 135 static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
 136 static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
 137 static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
 138 static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
 139 static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
 140 static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
 141 
 142 static struct attribute *ads7871_attrs[] = {
 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 ATTRIBUTE_GROUPS(ads7871);
 155 
 156 static int ads7871_probe(struct spi_device *spi)
 157 {
 158         struct device *dev = &spi->dev;
 159         int ret;
 160         uint8_t val;
 161         struct ads7871_data *pdata;
 162         struct device *hwmon_dev;
 163 
 164         /* Configure the SPI bus */
 165         spi->mode = (SPI_MODE_0);
 166         spi->bits_per_word = 8;
 167         spi_setup(spi);
 168 
 169         ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
 170         ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
 171 
 172         val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
 173         ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
 174         ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
 175 
 176         dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
 177         /*
 178          * because there is no other error checking on an SPI bus
 179          * we need to make sure we really have a chip
 180          */
 181         if (val != ret)
 182                 return -ENODEV;
 183 
 184         pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
 185         if (!pdata)
 186                 return -ENOMEM;
 187 
 188         pdata->spi = spi;
 189 
 190         hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
 191                                                            pdata,
 192                                                            ads7871_groups);
 193         return PTR_ERR_OR_ZERO(hwmon_dev);
 194 }
 195 
 196 static struct spi_driver ads7871_driver = {
 197         .driver = {
 198                 .name = DEVICE_NAME,
 199         },
 200         .probe = ads7871_probe,
 201 };
 202 
 203 module_spi_driver(ads7871_driver);
 204 
 205 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 206 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 207 MODULE_LICENSE("GPL");