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
65struct ads7871_data {
66	struct spi_device *spi;
67};
68
69static 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
77static 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
85static 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
91static 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
133static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
134static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
135static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
136static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
137static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
138static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
139static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
140static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
141
142static 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
154ATTRIBUTE_GROUPS(ads7871);
155
156static 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
196static struct spi_driver ads7871_driver = {
197	.driver = {
198		.name = DEVICE_NAME,
199	},
200	.probe = ads7871_probe,
201};
202
203module_spi_driver(ads7871_driver);
204
205MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
206MODULE_DESCRIPTION("TI ADS7871 A/D driver");
207MODULE_LICENSE("GPL");
208