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
ads7871_read_reg8(struct spi_device * spi,int reg)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
ads7871_read_reg16(struct spi_device * spi,int reg)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
ads7871_write_reg8(struct spi_device * spi,int reg,u8 val)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
voltage_show(struct device * dev,struct device_attribute * da,char * buf)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
ads7871_probe(struct spi_device * spi)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