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/mutex.h> 70 #include <linux/delay.h> 71 72 #define DEVICE_NAME "ads7871" 73 74 struct ads7871_data { 75 struct device *hwmon_dev; 76 struct mutex update_lock; 77 }; 78 79 static int ads7871_read_reg8(struct spi_device *spi, int reg) 80 { 81 int ret; 82 reg = reg | INST_READ_BM; 83 ret = spi_w8r8(spi, reg); 84 return ret; 85 } 86 87 static int ads7871_read_reg16(struct spi_device *spi, int reg) 88 { 89 int ret; 90 reg = reg | INST_READ_BM | INST_16BIT_BM; 91 ret = spi_w8r16(spi, reg); 92 return ret; 93 } 94 95 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val) 96 { 97 u8 tmp[2] = {reg, val}; 98 return spi_write(spi, tmp, sizeof(tmp)); 99 } 100 101 static ssize_t show_voltage(struct device *dev, 102 struct device_attribute *da, char *buf) 103 { 104 struct spi_device *spi = to_spi_device(dev); 105 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 106 int ret, val, i = 0; 107 uint8_t channel, mux_cnv; 108 109 channel = attr->index; 110 /* 111 * TODO: add support for conversions 112 * other than single ended with a gain of 1 113 */ 114 /*MUX_M3_BM forces single ended*/ 115 /*This is also where the gain of the PGA would be set*/ 116 ads7871_write_reg8(spi, REG_GAIN_MUX, 117 (MUX_CNV_BM | MUX_M3_BM | channel)); 118 119 ret = ads7871_read_reg8(spi, REG_GAIN_MUX); 120 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); 121 /* 122 * on 400MHz arm9 platform the conversion 123 * is already done when we do this test 124 */ 125 while ((i < 2) && mux_cnv) { 126 i++; 127 ret = ads7871_read_reg8(spi, REG_GAIN_MUX); 128 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); 129 msleep_interruptible(1); 130 } 131 132 if (mux_cnv == 0) { 133 val = ads7871_read_reg16(spi, REG_LS_BYTE); 134 /*result in volts*10000 = (val/8192)*2.5*10000*/ 135 val = ((val >> 2) * 25000) / 8192; 136 return sprintf(buf, "%d\n", val); 137 } else { 138 return -1; 139 } 140 } 141 142 static ssize_t ads7871_show_name(struct device *dev, 143 struct device_attribute *devattr, char *buf) 144 { 145 return sprintf(buf, "%s\n", to_spi_device(dev)->modalias); 146 } 147 148 static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0); 149 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1); 150 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2); 151 static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3); 152 static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4); 153 static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5); 154 static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6); 155 static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7); 156 157 static DEVICE_ATTR(name, S_IRUGO, ads7871_show_name, NULL); 158 159 static struct attribute *ads7871_attributes[] = { 160 &sensor_dev_attr_in0_input.dev_attr.attr, 161 &sensor_dev_attr_in1_input.dev_attr.attr, 162 &sensor_dev_attr_in2_input.dev_attr.attr, 163 &sensor_dev_attr_in3_input.dev_attr.attr, 164 &sensor_dev_attr_in4_input.dev_attr.attr, 165 &sensor_dev_attr_in5_input.dev_attr.attr, 166 &sensor_dev_attr_in6_input.dev_attr.attr, 167 &sensor_dev_attr_in7_input.dev_attr.attr, 168 &dev_attr_name.attr, 169 NULL 170 }; 171 172 static const struct attribute_group ads7871_group = { 173 .attrs = ads7871_attributes, 174 }; 175 176 static int ads7871_probe(struct spi_device *spi) 177 { 178 int ret, err; 179 uint8_t val; 180 struct ads7871_data *pdata; 181 182 dev_dbg(&spi->dev, "probe\n"); 183 184 /* Configure the SPI bus */ 185 spi->mode = (SPI_MODE_0); 186 spi->bits_per_word = 8; 187 spi_setup(spi); 188 189 ads7871_write_reg8(spi, REG_SER_CONTROL, 0); 190 ads7871_write_reg8(spi, REG_AD_CONTROL, 0); 191 192 val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM); 193 ads7871_write_reg8(spi, REG_OSC_CONTROL, val); 194 ret = ads7871_read_reg8(spi, REG_OSC_CONTROL); 195 196 dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret); 197 /* 198 * because there is no other error checking on an SPI bus 199 * we need to make sure we really have a chip 200 */ 201 if (val != ret) 202 return -ENODEV; 203 204 pdata = devm_kzalloc(&spi->dev, sizeof(struct ads7871_data), 205 GFP_KERNEL); 206 if (!pdata) 207 return -ENOMEM; 208 209 err = sysfs_create_group(&spi->dev.kobj, &ads7871_group); 210 if (err < 0) 211 return err; 212 213 spi_set_drvdata(spi, pdata); 214 215 pdata->hwmon_dev = hwmon_device_register(&spi->dev); 216 if (IS_ERR(pdata->hwmon_dev)) { 217 err = PTR_ERR(pdata->hwmon_dev); 218 goto error_remove; 219 } 220 221 return 0; 222 223 error_remove: 224 sysfs_remove_group(&spi->dev.kobj, &ads7871_group); 225 return err; 226 } 227 228 static int ads7871_remove(struct spi_device *spi) 229 { 230 struct ads7871_data *pdata = spi_get_drvdata(spi); 231 232 hwmon_device_unregister(pdata->hwmon_dev); 233 sysfs_remove_group(&spi->dev.kobj, &ads7871_group); 234 return 0; 235 } 236 237 static struct spi_driver ads7871_driver = { 238 .driver = { 239 .name = DEVICE_NAME, 240 .owner = THIS_MODULE, 241 }, 242 243 .probe = ads7871_probe, 244 .remove = ads7871_remove, 245 }; 246 247 module_spi_driver(ads7871_driver); 248 249 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>"); 250 MODULE_DESCRIPTION("TI ADS7871 A/D driver"); 251 MODULE_LICENSE("GPL"); 252