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