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#include <linux/of_device.h>
41
42
43#define DRVNAME		"lm70"
44
45#define LM70_CHIP_LM70		0	/* original NS LM70 */
46#define LM70_CHIP_TMP121	1	/* TI TMP121/TMP123 */
47#define LM70_CHIP_LM71		2	/* NS LM71 */
48#define LM70_CHIP_LM74		3	/* NS LM74 */
49
50struct lm70 {
51	struct spi_device *spi;
52	struct mutex lock;
53	unsigned int chip;
54};
55
56/* sysfs hook function */
57static ssize_t lm70_sense_temp(struct device *dev,
58		struct device_attribute *attr, char *buf)
59{
60	struct lm70 *p_lm70 = dev_get_drvdata(dev);
61	struct spi_device *spi = p_lm70->spi;
62	int status, val = 0;
63	u8 rxbuf[2];
64	s16 raw = 0;
65
66	if (mutex_lock_interruptible(&p_lm70->lock))
67		return -ERESTARTSYS;
68
69	/*
70	 * spi_read() requires a DMA-safe buffer; so we use
71	 * spi_write_then_read(), transmitting 0 bytes.
72	 */
73	status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
74	if (status < 0) {
75		pr_warn("spi_write_then_read failed with status %d\n", status);
76		goto out;
77	}
78	raw = (rxbuf[0] << 8) + rxbuf[1];
79	dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
80		rxbuf[0], rxbuf[1], raw);
81
82	/*
83	 * LM70:
84	 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
85	 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
86	 * bits) are meaningful; the LSB 5 bits are to be discarded.
87	 * See the datasheet.
88	 *
89	 * Further, each bit represents 0.25 degrees Celsius; so, multiply
90	 * by 0.25. Also multiply by 1000 to represent in millidegrees
91	 * Celsius.
92	 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
93	 *
94	 * LM74 and TMP121/TMP123:
95	 * 13 bits of 2's complement data, discard LSB 3 bits,
96	 * resolution 0.0625 degrees celsius.
97	 *
98	 * LM71:
99	 * 14 bits of 2's complement data, discard LSB 2 bits,
100	 * resolution 0.0312 degrees celsius.
101	 */
102	switch (p_lm70->chip) {
103	case LM70_CHIP_LM70:
104		val = ((int)raw / 32) * 250;
105		break;
106
107	case LM70_CHIP_TMP121:
108	case LM70_CHIP_LM74:
109		val = ((int)raw / 8) * 625 / 10;
110		break;
111
112	case LM70_CHIP_LM71:
113		val = ((int)raw / 4) * 3125 / 100;
114		break;
115	}
116
117	status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
118out:
119	mutex_unlock(&p_lm70->lock);
120	return status;
121}
122
123static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
124
125static struct attribute *lm70_attrs[] = {
126	&dev_attr_temp1_input.attr,
127	NULL
128};
129
130ATTRIBUTE_GROUPS(lm70);
131
132/*----------------------------------------------------------------------*/
133
134#ifdef CONFIG_OF
135static const struct of_device_id lm70_of_ids[] = {
136	{
137		.compatible = "ti,lm70",
138		.data = (void *) LM70_CHIP_LM70,
139	},
140	{
141		.compatible = "ti,tmp121",
142		.data = (void *) LM70_CHIP_TMP121,
143	},
144	{
145		.compatible = "ti,lm71",
146		.data = (void *) LM70_CHIP_LM71,
147	},
148	{
149		.compatible = "ti,lm74",
150		.data = (void *) LM70_CHIP_LM74,
151	},
152	{},
153};
154MODULE_DEVICE_TABLE(of, lm70_of_ids);
155#endif
156
157static int lm70_probe(struct spi_device *spi)
158{
159	const struct of_device_id *match;
160	struct device *hwmon_dev;
161	struct lm70 *p_lm70;
162	int chip;
163
164	match = of_match_device(lm70_of_ids, &spi->dev);
165	if (match)
166		chip = (int)(uintptr_t)match->data;
167	else
168		chip = spi_get_device_id(spi)->driver_data;
169
170	/* signaling is SPI_MODE_0 */
171	if (spi->mode & (SPI_CPOL | SPI_CPHA))
172		return -EINVAL;
173
174	/* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
175
176	p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
177	if (!p_lm70)
178		return -ENOMEM;
179
180	mutex_init(&p_lm70->lock);
181	p_lm70->chip = chip;
182	p_lm70->spi = spi;
183
184	hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
185							   spi->modalias,
186							   p_lm70, lm70_groups);
187	return PTR_ERR_OR_ZERO(hwmon_dev);
188}
189
190static const struct spi_device_id lm70_ids[] = {
191	{ "lm70",   LM70_CHIP_LM70 },
192	{ "tmp121", LM70_CHIP_TMP121 },
193	{ "lm71",   LM70_CHIP_LM71 },
194	{ "lm74",   LM70_CHIP_LM74 },
195	{ },
196};
197MODULE_DEVICE_TABLE(spi, lm70_ids);
198
199static struct spi_driver lm70_driver = {
200	.driver = {
201		.name	= "lm70",
202		.of_match_table	= of_match_ptr(lm70_of_ids),
203	},
204	.id_table = lm70_ids,
205	.probe	= lm70_probe,
206};
207
208module_spi_driver(lm70_driver);
209
210MODULE_AUTHOR("Kaiwan N Billimoria");
211MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
212MODULE_LICENSE("GPL");
213