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
ads7871_read_reg8(struct spi_device * spi,int reg)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
ads7871_read_reg16(struct spi_device * spi,int reg)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
ads7871_write_reg8(struct spi_device * spi,int reg,u8 val)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
show_voltage(struct device * dev,struct device_attribute * da,char * buf)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
ads7871_show_name(struct device * dev,struct device_attribute * devattr,char * buf)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
ads7871_probe(struct spi_device * spi)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
ads7871_remove(struct spi_device * spi)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