drivers/hwmon/ads7871.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *  ads7871 - driver for TI ADS7871 A/D converter
0004  *
0005  *  Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
0006  *
0007  *  You need to have something like this in struct spi_board_info
0008  *  {
0009  *      .modalias   = "ads7871",
0010  *      .max_speed_hz   = 2*1000*1000,
0011  *      .chip_select    = 0,
0012  *      .bus_num    = 1,
0013  *  },
0014  */
0015
0016 /*From figure 18 in the datasheet*/
0017 /*Register addresses*/
0018 #define REG_LS_BYTE 0 /*A/D Output Data, LS Byte*/
0019 #define REG_MS_BYTE 1 /*A/D Output Data, MS Byte*/
0020 #define REG_PGA_VALID   2 /*PGA Valid Register*/
0021 #define REG_AD_CONTROL  3 /*A/D Control Register*/
0022 #define REG_GAIN_MUX    4 /*Gain/Mux Register*/
0023 #define REG_IO_STATE    5 /*Digital I/O State Register*/
0024 #define REG_IO_CONTROL  6 /*Digital I/O Control Register*/
0025 #define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
0026 #define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
0027 #define REG_ID      31 /*ID Register*/
0028
0029 /*
0030  * From figure 17 in the datasheet
0031  * These bits get ORed with the address to form
0032  * the instruction byte
0033  */
0034 /*Instruction Bit masks*/
0035 #define INST_MODE_BM    (1 << 7)
0036 #define INST_READ_BM    (1 << 6)
0037 #define INST_16BIT_BM   (1 << 5)
0038
0039 /*From figure 18 in the datasheet*/
0040 /*bit masks for Rev/Oscillator Control Register*/
0041 #define MUX_CNV_BV  7
0042 #define MUX_CNV_BM  (1 << MUX_CNV_BV)
0043 #define MUX_M3_BM   (1 << 3) /*M3 selects single ended*/
0044 #define MUX_G_BV    4 /*allows for reg = (gain << MUX_G_BV) | ...*/
0045
0046 /*From figure 18 in the datasheet*/
0047 /*bit masks for Rev/Oscillator Control Register*/
0048 #define OSC_OSCR_BM (1 << 5)
0049 #define OSC_OSCE_BM (1 << 4)
0050 #define OSC_REFE_BM (1 << 3)
0051 #define OSC_BUFE_BM (1 << 2)
0052 #define OSC_R2V_BM  (1 << 1)
0053 #define OSC_RBG_BM  (1 << 0)
0054
0055 #include <linux/module.h>
0056 #include <linux/init.h>
0057 #include <linux/spi/spi.h>
0058 #include <linux/hwmon.h>
0059 #include <linux/hwmon-sysfs.h>
0060 #include <linux/err.h>
0061 #include <linux/delay.h>
0062
0063 #define DEVICE_NAME "ads7871"
0064
0065 struct ads7871_data {
0066     struct spi_device *spi;
0067 };
0068
0069 static int ads7871_read_reg8(struct spi_device *spi, int reg)
0070 {
0071     int ret;
0072     reg = reg | INST_READ_BM;
0073     ret = spi_w8r8(spi, reg);
0074     return ret;
0075 }
0076
0077 static int ads7871_read_reg16(struct spi_device *spi, int reg)
0078 {
0079     int ret;
0080     reg = reg | INST_READ_BM | INST_16BIT_BM;
0081     ret = spi_w8r16(spi, reg);
0082     return ret;
0083 }
0084
0085 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
0086 {
0087     u8 tmp[2] = {reg, val};
0088     return spi_write(spi, tmp, sizeof(tmp));
0089 }
0090
0091 static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
0092                 char *buf)
0093 {
0094     struct ads7871_data *pdata = dev_get_drvdata(dev);
0095     struct spi_device *spi = pdata->spi;
0096     struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
0097     int ret, val, i = 0;
0098     uint8_t channel, mux_cnv;
0099
0100     channel = attr->index;
0101     /*
0102      * TODO: add support for conversions
0103      * other than single ended with a gain of 1
0104      */
0105     /*MUX_M3_BM forces single ended*/
0106     /*This is also where the gain of the PGA would be set*/
0107     ads7871_write_reg8(spi, REG_GAIN_MUX,
0108         (MUX_CNV_BM | MUX_M3_BM | channel));
0109
0110     ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
0111     mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
0112     /*
0113      * on 400MHz arm9 platform the conversion
0114      * is already done when we do this test
0115      */
0116     while ((i < 2) && mux_cnv) {
0117         i++;
0118         ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
0119         mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
0120         msleep_interruptible(1);
0121     }
0122
0123     if (mux_cnv == 0) {
0124         val = ads7871_read_reg16(spi, REG_LS_BYTE);
0125         /*result in volts*10000 = (val/8192)*2.5*10000*/
0126         val = ((val >> 2) * 25000) / 8192;
0127         return sprintf(buf, "%d\n", val);
0128     } else {
0129         return -1;
0130     }
0131 }
0132
0133 static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
0134 static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
0135 static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
0136 static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
0137 static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
0138 static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
0139 static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
0140 static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
0141
0142 static struct attribute *ads7871_attrs[] = {
0143     &sensor_dev_attr_in0_input.dev_attr.attr,
0144     &sensor_dev_attr_in1_input.dev_attr.attr,
0145     &sensor_dev_attr_in2_input.dev_attr.attr,
0146     &sensor_dev_attr_in3_input.dev_attr.attr,
0147     &sensor_dev_attr_in4_input.dev_attr.attr,
0148     &sensor_dev_attr_in5_input.dev_attr.attr,
0149     &sensor_dev_attr_in6_input.dev_attr.attr,
0150     &sensor_dev_attr_in7_input.dev_attr.attr,
0151     NULL
0152 };
0153
0154 ATTRIBUTE_GROUPS(ads7871);
0155
0156 static int ads7871_probe(struct spi_device *spi)
0157 {
0158     struct device *dev = &spi->dev;
0159     int ret;
0160     uint8_t val;
0161     struct ads7871_data *pdata;
0162     struct device *hwmon_dev;
0163
0164     /* Configure the SPI bus */
0165     spi->mode = (SPI_MODE_0);
0166     spi->bits_per_word = 8;
0167     spi_setup(spi);
0168
0169     ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
0170     ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
0171
0172     val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
0173     ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
0174     ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
0175
0176     dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
0177     /*
0178      * because there is no other error checking on an SPI bus
0179      * we need to make sure we really have a chip
0180      */
0181     if (val != ret)
0182         return -ENODEV;
0183
0184     pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
0185     if (!pdata)
0186         return -ENOMEM;
0187
0188     pdata->spi = spi;
0189
0190     hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
0191                                pdata,
0192                                ads7871_groups);
0193     return PTR_ERR_OR_ZERO(hwmon_dev);
0194 }
0195
0196 static struct spi_driver ads7871_driver = {
0197     .driver = {
0198         .name = DEVICE_NAME,
0199     },
0200     .probe = ads7871_probe,
0201 };
0202
0203 module_spi_driver(ads7871_driver);
0204
0205 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
0206 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
0207 MODULE_LICENSE("GPL");