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/*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
  72struct ads7871_data {
  73        struct device   *hwmon_dev;
  74        struct mutex    update_lock;
  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 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
 136static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
 137static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
 138static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
 139static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
 140static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
 141static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
 142static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
 143static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
 144
 145static 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
 157static const struct attribute_group ads7871_group = {
 158        .attrs = ads7871_attributes,
 159};
 160
 161static int __devinit ads7871_probe(struct spi_device *spi)
 162{
 163        int ret, err;
 164        uint8_t val;
 165        struct ads7871_data *pdata;
 166
 167        dev_dbg(&spi->dev, "probe\n");
 168
 169        /* Configure the SPI bus */
 170        spi->mode = (SPI_MODE_0);
 171        spi->bits_per_word = 8;
 172        spi_setup(spi);
 173
 174        ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
 175        ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
 176
 177        val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm);
 178        ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
 179        ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
 180
 181        dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
 182        /*because there is no other error checking on an SPI bus
 183        we need to make sure we really have a chip*/
 184        if (val != ret) {
 185                err = -ENODEV;
 186                goto exit;
 187        }
 188
 189        pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL);
 190        if (!pdata) {
 191                err = -ENOMEM;
 192                goto exit;
 193        }
 194
 195        err = sysfs_create_group(&spi->dev.kobj, &ads7871_group);
 196        if (err < 0)
 197                goto error_free;
 198
 199        spi_set_drvdata(spi, pdata);
 200
 201        pdata->hwmon_dev = hwmon_device_register(&spi->dev);
 202        if (IS_ERR(pdata->hwmon_dev)) {
 203                err = PTR_ERR(pdata->hwmon_dev);
 204                goto error_remove;
 205        }
 206
 207        return 0;
 208
 209error_remove:
 210        sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
 211error_free:
 212        kfree(pdata);
 213exit:
 214        return err;
 215}
 216
 217static 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
 227static 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
 238static int __init ads7871_init(void)
 239{
 240        return spi_register_driver(&ads7871_driver);
 241}
 242
 243static void __exit ads7871_exit(void)
 244{
 245        spi_unregister_driver(&ads7871_driver);
 246}
 247
 248module_init(ads7871_init);
 249module_exit(ads7871_exit);
 250
 251MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
 252MODULE_DESCRIPTION("TI ADS7871 A/D driver");
 253MODULE_LICENSE("GPL");
 254