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
81 reg = reg | INST_READ_BM | INST_16BIT_BM;
82 ret = spi_w8r16(spi, reg);
83 if (ret < 0)
84 return ret;
85
86 return le16_to_cpu((__force __le16)ret);
87 }
88
ads7871_write_reg8(struct spi_device * spi,int reg,u8 val)89 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
90 {
91 u8 tmp[2] = {reg, val};
92 return spi_write(spi, tmp, sizeof(tmp));
93 }
94
voltage_show(struct device * dev,struct device_attribute * da,char * buf)95 static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
96 char *buf)
97 {
98 struct ads7871_data *pdata = dev_get_drvdata(dev);
99 struct spi_device *spi = pdata->spi;
100 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
101 int ret, val, i = 0;
102 uint8_t channel, mux_cnv;
103
104 channel = attr->index;
105 /*
106 * TODO: add support for conversions
107 * other than single ended with a gain of 1
108 */
109 /*MUX_M3_BM forces single ended*/
110 /*This is also where the gain of the PGA would be set*/
111 ret = ads7871_write_reg8(spi, REG_GAIN_MUX,
112 (MUX_CNV_BM | MUX_M3_BM | channel));
113 if (ret < 0)
114 return ret;
115
116 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
117 if (ret < 0)
118 return ret;
119 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
120 /*
121 * on 400MHz arm9 platform the conversion
122 * is already done when we do this test
123 */
124 while ((i < 2) && mux_cnv) {
125 i++;
126 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
127 if (ret < 0)
128 return ret;
129 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
130 msleep_interruptible(1);
131 }
132
133 if (mux_cnv == 0) {
134 val = ads7871_read_reg16(spi, REG_LS_BYTE);
135 if (val < 0)
136 return val;
137 /*result in volts*10000 = (val/8192)*2.5*10000*/
138 val = ((val >> 2) * 25000) / 8192;
139 return sysfs_emit(buf, "%d\n", val);
140 }
141
142 return -ETIMEDOUT;
143 }
144
145 static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
146 static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
147 static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
148 static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
149 static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
150 static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
151 static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
152 static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
153
154 static struct attribute *ads7871_attrs[] = {
155 &sensor_dev_attr_in0_input.dev_attr.attr,
156 &sensor_dev_attr_in1_input.dev_attr.attr,
157 &sensor_dev_attr_in2_input.dev_attr.attr,
158 &sensor_dev_attr_in3_input.dev_attr.attr,
159 &sensor_dev_attr_in4_input.dev_attr.attr,
160 &sensor_dev_attr_in5_input.dev_attr.attr,
161 &sensor_dev_attr_in6_input.dev_attr.attr,
162 &sensor_dev_attr_in7_input.dev_attr.attr,
163 NULL
164 };
165
166 ATTRIBUTE_GROUPS(ads7871);
167
ads7871_probe(struct spi_device * spi)168 static int ads7871_probe(struct spi_device *spi)
169 {
170 struct device *dev = &spi->dev;
171 int ret;
172 uint8_t val;
173 struct ads7871_data *pdata;
174 struct device *hwmon_dev;
175
176 /* Configure the SPI bus */
177 spi->mode = (SPI_MODE_0);
178 spi->bits_per_word = 8;
179 spi_setup(spi);
180
181 ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
182 ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
183
184 val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
185 ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
186 ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
187
188 dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
189 /*
190 * because there is no other error checking on an SPI bus
191 * we need to make sure we really have a chip
192 */
193 if (val != ret)
194 return -ENODEV;
195
196 pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
197 if (!pdata)
198 return -ENOMEM;
199
200 pdata->spi = spi;
201
202 hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
203 pdata,
204 ads7871_groups);
205 return PTR_ERR_OR_ZERO(hwmon_dev);
206 }
207
208 static struct spi_driver ads7871_driver = {
209 .driver = {
210 .name = DEVICE_NAME,
211 },
212 .probe = ads7871_probe,
213 };
214
215 module_spi_driver(ads7871_driver);
216
217 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
218 MODULE_DESCRIPTION("TI ADS7871 A/D driver");
219 MODULE_LICENSE("GPL");
220