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"); 208