1/*
2 * drivers/hwmon/nsa320-hwmon.c
3 *
4 * ZyXEL NSA320 Media Servers
5 * hardware monitoring
6 *
7 * Copyright (C) 2016 Adam Baker <linux@baker-net.org.uk>
8 * based on a board file driver
9 * Copyright (C) 2012 Peter Schildmann <linux@schildmann.info>
10 *
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License v2 as published by the
13 * Free Software Foundation.
14 *
15 * This program is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
18 * more details.
19 */
20
21#include <linux/bitops.h>
22#include <linux/delay.h>
23#include <linux/err.h>
24#include <linux/gpio/consumer.h>
25#include <linux/hwmon.h>
26#include <linux/hwmon-sysfs.h>
27#include <linux/jiffies.h>
28#include <linux/module.h>
29#include <linux/mutex.h>
30#include <linux/of.h>
31#include <linux/of_device.h>
32#include <linux/of_platform.h>
33#include <linux/platform_device.h>
34
35/* Tests for error return values rely upon this value being < 0x80 */
36#define MAGIC_NUMBER 0x55
37
38/*
39 * The Zyxel hwmon MCU is a Holtek HT46R065 that is factory programmed
40 * to perform temperature and fan speed monitoring. It is read by taking
41 * the active pin low. The 32 bit output word is then clocked onto the
42 * data line. The MSB of the data word is a magic nuber to indicate it
43 * has been read correctly, the next byte is the fan speed (in hundreds
44 * of RPM) and the last two bytes are the temperature (in tenths of a
45 * degree)
46 */
47
48struct nsa320_hwmon {
49 struct mutex update_lock; /* lock GPIO operations */
50 unsigned long last_updated; /* jiffies */
51 unsigned long mcu_data;
52 struct gpio_desc *act;
53 struct gpio_desc *clk;
54 struct gpio_desc *data;
55};
56
57enum nsa320_inputs {
58 NSA320_TEMP = 0,
59 NSA320_FAN = 1,
60};
61
62static const char * const nsa320_input_names[] = {
63 [NSA320_TEMP] = "System Temperature",
64 [NSA320_FAN] = "Chassis Fan",
65};
66
67/*
68 * Although this protocol looks similar to SPI the long delay
69 * between the active (aka chip select) signal and the shorter
70 * delay between clock pulses are needed for reliable operation.
71 * The delays provided are taken from the manufacturer kernel,
72 * testing suggest they probably incorporate a reasonable safety
73 * margin. (The single device tested became unreliable if the
74 * delay was reduced to 1/10th of this value.)
75 */
76static s32 nsa320_hwmon_update(struct device *dev)
77{
78 u32 mcu_data;
79 u32 mask;
80 struct nsa320_hwmon *hwmon = dev_get_drvdata(dev);
81
82 mutex_lock(&hwmon->update_lock);
83
84 mcu_data = hwmon->mcu_data;
85
86 if (time_after(jiffies, hwmon->last_updated + HZ) || mcu_data == 0) {
87 gpiod_set_value(hwmon->act, 1);
88 msleep(100);
89
90 mcu_data = 0;
91 for (mask = BIT(31); mask; mask >>= 1) {
92 gpiod_set_value(hwmon->clk, 0);
93 usleep_range(100, 200);
94 gpiod_set_value(hwmon->clk, 1);
95 usleep_range(100, 200);
96 if (gpiod_get_value(hwmon->data))
97 mcu_data |= mask;
98 }
99
100 gpiod_set_value(hwmon->act, 0);
101 dev_dbg(dev, "Read raw MCU data %08x\n", mcu_data);
102
103 if ((mcu_data >> 24) != MAGIC_NUMBER) {
104 dev_dbg(dev, "Read invalid MCU data %08x\n", mcu_data);
105 mcu_data = -EIO;
106 } else {
107 hwmon->mcu_data = mcu_data;
108 hwmon->last_updated = jiffies;
109 }
110 }
111
112 mutex_unlock(&hwmon->update_lock);
113
114 return mcu_data;
115}
116
117static ssize_t label_show(struct device *dev, struct device_attribute *attr,
118 char *buf)
119{
120 int channel = to_sensor_dev_attr(attr)->index;
121
122 return sprintf(buf, "%s\n", nsa320_input_names[channel]);
123}
124
125static ssize_t temp1_input_show(struct device *dev,
126 struct device_attribute *attr, char *buf)
127{
128 s32 mcu_data = nsa320_hwmon_update(dev);
129
130 if (mcu_data < 0)
131 return mcu_data;
132
133 return sprintf(buf, "%d\n", (mcu_data & 0xffff) * 100);
134}
135
136static ssize_t fan1_input_show(struct device *dev,
137 struct device_attribute *attr, char *buf)
138{
139 s32 mcu_data = nsa320_hwmon_update(dev);
140
141 if (mcu_data < 0)
142 return mcu_data;
143
144 return sprintf(buf, "%d\n", ((mcu_data & 0xff0000) >> 16) * 100);
145}
146
147static SENSOR_DEVICE_ATTR_RO(temp1_label, label, NSA320_TEMP);
148static DEVICE_ATTR_RO(temp1_input);
149static SENSOR_DEVICE_ATTR_RO(fan1_label, label, NSA320_FAN);
150static DEVICE_ATTR_RO(fan1_input);
151
152static struct attribute *nsa320_attrs[] = {
153 &sensor_dev_attr_temp1_label.dev_attr.attr,
154 &dev_attr_temp1_input.attr,
155 &sensor_dev_attr_fan1_label.dev_attr.attr,
156 &dev_attr_fan1_input.attr,
157 NULL
158};
159
160ATTRIBUTE_GROUPS(nsa320);
161
162static const struct of_device_id of_nsa320_hwmon_match[] = {
163 { .compatible = "zyxel,nsa320-mcu", },
164 { },
165};
166
167static int nsa320_hwmon_probe(struct platform_device *pdev)
168{
169 struct nsa320_hwmon *hwmon;
170 struct device *classdev;
171
172 hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
173 if (!hwmon)
174 return -ENOMEM;
175
176 /* Look up the GPIO pins to use */
177 hwmon->act = devm_gpiod_get(&pdev->dev, "act", GPIOD_OUT_LOW);
178 if (IS_ERR(hwmon->act))
179 return PTR_ERR(hwmon->act);
180
181 hwmon->clk = devm_gpiod_get(&pdev->dev, "clk", GPIOD_OUT_HIGH);
182 if (IS_ERR(hwmon->clk))
183 return PTR_ERR(hwmon->clk);
184
185 hwmon->data = devm_gpiod_get(&pdev->dev, "data", GPIOD_IN);
186 if (IS_ERR(hwmon->data))
187 return PTR_ERR(hwmon->data);
188
189 mutex_init(&hwmon->update_lock);
190
191 classdev = devm_hwmon_device_register_with_groups(&pdev->dev,
192 "nsa320", hwmon, nsa320_groups);
193
194 return PTR_ERR_OR_ZERO(classdev);
195
196}
197
198/* All allocations use devres so remove() is not needed. */
199
200static struct platform_driver nsa320_hwmon_driver = {
201 .probe = nsa320_hwmon_probe,
202 .driver = {
203 .name = "nsa320-hwmon",
204 .of_match_table = of_match_ptr(of_nsa320_hwmon_match),
205 },
206};
207
208module_platform_driver(nsa320_hwmon_driver);
209
210MODULE_DEVICE_TABLE(of, of_nsa320_hwmon_match);
211MODULE_AUTHOR("Peter Schildmann <linux@schildmann.info>");
212MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>");
213MODULE_DESCRIPTION("NSA320 Hardware Monitoring");
214MODULE_LICENSE("GPL v2");
215MODULE_ALIAS("platform:nsa320-hwmon");
216