xref: /openbmc/linux/drivers/hwmon/lm70.c (revision d2999e1b)
1 /*
2  * lm70.c
3  *
4  * The LM70 is a temperature sensor chip from National Semiconductor (NS).
5  * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
6  *
7  * The LM70 communicates with a host processor via an SPI/Microwire Bus
8  * interface. The complete datasheet is available at National's website
9  * here:
10  * http://www.national.com/pf/LM/LM70.html
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU General Public License as published by
14  * the Free Software Foundation; either version 2 of the License, or
15  * (at your option) any later version.
16  *
17  * This program is distributed in the hope that it will be useful,
18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20  * GNU General Public License for more details.
21  *
22  * You should have received a copy of the GNU General Public License
23  * along with this program; if not, write to the Free Software
24  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
25  */
26 
27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28 
29 #include <linux/init.h>
30 #include <linux/module.h>
31 #include <linux/kernel.h>
32 #include <linux/device.h>
33 #include <linux/err.h>
34 #include <linux/sysfs.h>
35 #include <linux/hwmon.h>
36 #include <linux/mutex.h>
37 #include <linux/mod_devicetable.h>
38 #include <linux/spi/spi.h>
39 #include <linux/slab.h>
40 
41 
42 #define DRVNAME		"lm70"
43 
44 #define LM70_CHIP_LM70		0	/* original NS LM70 */
45 #define LM70_CHIP_TMP121	1	/* TI TMP121/TMP123 */
46 #define LM70_CHIP_LM71		2	/* NS LM71 */
47 #define LM70_CHIP_LM74		3	/* NS LM74 */
48 
49 struct lm70 {
50 	struct spi_device *spi;
51 	struct mutex lock;
52 	unsigned int chip;
53 };
54 
55 /* sysfs hook function */
56 static ssize_t lm70_sense_temp(struct device *dev,
57 		struct device_attribute *attr, char *buf)
58 {
59 	struct lm70 *p_lm70 = dev_get_drvdata(dev);
60 	struct spi_device *spi = p_lm70->spi;
61 	int status, val = 0;
62 	u8 rxbuf[2];
63 	s16 raw = 0;
64 
65 	if (mutex_lock_interruptible(&p_lm70->lock))
66 		return -ERESTARTSYS;
67 
68 	/*
69 	 * spi_read() requires a DMA-safe buffer; so we use
70 	 * spi_write_then_read(), transmitting 0 bytes.
71 	 */
72 	status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
73 	if (status < 0) {
74 		pr_warn("spi_write_then_read failed with status %d\n", status);
75 		goto out;
76 	}
77 	raw = (rxbuf[0] << 8) + rxbuf[1];
78 	dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
79 		rxbuf[0], rxbuf[1], raw);
80 
81 	/*
82 	 * LM70:
83 	 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
84 	 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
85 	 * bits) are meaningful; the LSB 5 bits are to be discarded.
86 	 * See the datasheet.
87 	 *
88 	 * Further, each bit represents 0.25 degrees Celsius; so, multiply
89 	 * by 0.25. Also multiply by 1000 to represent in millidegrees
90 	 * Celsius.
91 	 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
92 	 *
93 	 * LM74 and TMP121/TMP123:
94 	 * 13 bits of 2's complement data, discard LSB 3 bits,
95 	 * resolution 0.0625 degrees celsius.
96 	 *
97 	 * LM71:
98 	 * 14 bits of 2's complement data, discard LSB 2 bits,
99 	 * resolution 0.0312 degrees celsius.
100 	 */
101 	switch (p_lm70->chip) {
102 	case LM70_CHIP_LM70:
103 		val = ((int)raw / 32) * 250;
104 		break;
105 
106 	case LM70_CHIP_TMP121:
107 	case LM70_CHIP_LM74:
108 		val = ((int)raw / 8) * 625 / 10;
109 		break;
110 
111 	case LM70_CHIP_LM71:
112 		val = ((int)raw / 4) * 3125 / 100;
113 		break;
114 	}
115 
116 	status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
117 out:
118 	mutex_unlock(&p_lm70->lock);
119 	return status;
120 }
121 
122 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
123 
124 static struct attribute *lm70_attrs[] = {
125 	&dev_attr_temp1_input.attr,
126 	NULL
127 };
128 
129 ATTRIBUTE_GROUPS(lm70);
130 
131 /*----------------------------------------------------------------------*/
132 
133 static int lm70_probe(struct spi_device *spi)
134 {
135 	int chip = spi_get_device_id(spi)->driver_data;
136 	struct device *hwmon_dev;
137 	struct lm70 *p_lm70;
138 
139 	/* signaling is SPI_MODE_0 */
140 	if (spi->mode & (SPI_CPOL | SPI_CPHA))
141 		return -EINVAL;
142 
143 	/* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
144 
145 	p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
146 	if (!p_lm70)
147 		return -ENOMEM;
148 
149 	mutex_init(&p_lm70->lock);
150 	p_lm70->chip = chip;
151 	p_lm70->spi = spi;
152 
153 	hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
154 							   spi->modalias,
155 							   p_lm70, lm70_groups);
156 	return PTR_ERR_OR_ZERO(hwmon_dev);
157 }
158 
159 static const struct spi_device_id lm70_ids[] = {
160 	{ "lm70",   LM70_CHIP_LM70 },
161 	{ "tmp121", LM70_CHIP_TMP121 },
162 	{ "lm71",   LM70_CHIP_LM71 },
163 	{ "lm74",   LM70_CHIP_LM74 },
164 	{ },
165 };
166 MODULE_DEVICE_TABLE(spi, lm70_ids);
167 
168 static struct spi_driver lm70_driver = {
169 	.driver = {
170 		.name	= "lm70",
171 		.owner	= THIS_MODULE,
172 	},
173 	.id_table = lm70_ids,
174 	.probe	= lm70_probe,
175 };
176 
177 module_spi_driver(lm70_driver);
178 
179 MODULE_AUTHOR("Kaiwan N Billimoria");
180 MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
181 MODULE_LICENSE("GPL");
182