LXR linux/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
  73struct ads7871_data {
  74        struct spi_device *spi;
  75};
  76
  77static 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
  85static 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
  93static 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
  99static 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
 141static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
 142static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
 143static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
 144static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
 145static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
 146static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
 147static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
 148static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
 149
 150static 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
 162ATTRIBUTE_GROUPS(ads7871);
 163
 164static 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
 204static struct spi_driver ads7871_driver = {
 205        .driver = {
 206                .name = DEVICE_NAME,
 207        },
 208        .probe = ads7871_probe,
 209};
 210
 211module_spi_driver(ads7871_driver);
 212
 213MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 214MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 215MODULE_LICENSE("GPL");
 216