xref: /openbmc/linux/drivers/hwmon/ads7871.c (revision aec89d29)
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