xref: /openbmc/linux/drivers/hwmon/nsa320-hwmon.c (revision 7d9be29d)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * drivers/hwmon/nsa320-hwmon.c
4  *
5  * ZyXEL NSA320 Media Servers
6  * hardware monitoring
7  *
8  * Copyright (C) 2016 Adam Baker <linux@baker-net.org.uk>
9  * based on a board file driver
10  * Copyright (C) 2012 Peter Schildmann <linux@schildmann.info>
11  */
12 
13 #include <linux/bitops.h>
14 #include <linux/delay.h>
15 #include <linux/err.h>
16 #include <linux/gpio/consumer.h>
17 #include <linux/hwmon.h>
18 #include <linux/hwmon-sysfs.h>
19 #include <linux/jiffies.h>
20 #include <linux/module.h>
21 #include <linux/mutex.h>
22 #include <linux/of.h>
23 #include <linux/platform_device.h>
24 
25 /* Tests for error return values rely upon this value being < 0x80 */
26 #define MAGIC_NUMBER 0x55
27 
28 /*
29  * The Zyxel hwmon MCU is a Holtek HT46R065 that is factory programmed
30  * to perform temperature and fan speed monitoring. It is read by taking
31  * the active pin low. The 32 bit output word is then clocked onto the
32  * data line. The MSB of the data word is a magic nuber to indicate it
33  * has been read correctly, the next byte is the fan speed (in hundreds
34  * of RPM) and the last two bytes are the temperature (in tenths of a
35  * degree)
36  */
37 
38 struct nsa320_hwmon {
39 	struct mutex		update_lock;	/* lock GPIO operations */
40 	unsigned long		last_updated;	/* jiffies */
41 	unsigned long		mcu_data;
42 	struct gpio_desc	*act;
43 	struct gpio_desc	*clk;
44 	struct gpio_desc	*data;
45 };
46 
47 enum nsa320_inputs {
48 	NSA320_TEMP = 0,
49 	NSA320_FAN = 1,
50 };
51 
52 static const char * const nsa320_input_names[] = {
53 	[NSA320_TEMP] = "System Temperature",
54 	[NSA320_FAN] = "Chassis Fan",
55 };
56 
57 /*
58  * Although this protocol looks similar to SPI the long delay
59  * between the active (aka chip select) signal and the shorter
60  * delay between clock pulses are needed for reliable operation.
61  * The delays provided are taken from the manufacturer kernel,
62  * testing suggest they probably incorporate a reasonable safety
63  * margin. (The single device tested became unreliable if the
64  * delay was reduced to 1/10th of this value.)
65  */
nsa320_hwmon_update(struct device * dev)66 static s32 nsa320_hwmon_update(struct device *dev)
67 {
68 	u32 mcu_data;
69 	u32 mask;
70 	struct nsa320_hwmon *hwmon = dev_get_drvdata(dev);
71 
72 	mutex_lock(&hwmon->update_lock);
73 
74 	mcu_data = hwmon->mcu_data;
75 
76 	if (time_after(jiffies, hwmon->last_updated + HZ) || mcu_data == 0) {
77 		gpiod_set_value(hwmon->act, 1);
78 		msleep(100);
79 
80 		mcu_data = 0;
81 		for (mask = BIT(31); mask; mask >>= 1) {
82 			gpiod_set_value(hwmon->clk, 0);
83 			usleep_range(100, 200);
84 			gpiod_set_value(hwmon->clk, 1);
85 			usleep_range(100, 200);
86 			if (gpiod_get_value(hwmon->data))
87 				mcu_data |= mask;
88 		}
89 
90 		gpiod_set_value(hwmon->act, 0);
91 		dev_dbg(dev, "Read raw MCU data %08x\n", mcu_data);
92 
93 		if ((mcu_data >> 24) != MAGIC_NUMBER) {
94 			dev_dbg(dev, "Read invalid MCU data %08x\n", mcu_data);
95 			mcu_data = -EIO;
96 		} else {
97 			hwmon->mcu_data = mcu_data;
98 			hwmon->last_updated = jiffies;
99 		}
100 	}
101 
102 	mutex_unlock(&hwmon->update_lock);
103 
104 	return mcu_data;
105 }
106 
label_show(struct device * dev,struct device_attribute * attr,char * buf)107 static ssize_t label_show(struct device *dev, struct device_attribute *attr,
108 			  char *buf)
109 {
110 	int channel = to_sensor_dev_attr(attr)->index;
111 
112 	return sprintf(buf, "%s\n", nsa320_input_names[channel]);
113 }
114 
temp1_input_show(struct device * dev,struct device_attribute * attr,char * buf)115 static ssize_t temp1_input_show(struct device *dev,
116 				struct device_attribute *attr, char *buf)
117 {
118 	s32 mcu_data = nsa320_hwmon_update(dev);
119 
120 	if (mcu_data < 0)
121 		return mcu_data;
122 
123 	return sprintf(buf, "%d\n", (mcu_data & 0xffff) * 100);
124 }
125 
fan1_input_show(struct device * dev,struct device_attribute * attr,char * buf)126 static ssize_t fan1_input_show(struct device *dev,
127 			       struct device_attribute *attr, char *buf)
128 {
129 	s32 mcu_data = nsa320_hwmon_update(dev);
130 
131 	if (mcu_data < 0)
132 		return mcu_data;
133 
134 	return sprintf(buf, "%d\n", ((mcu_data & 0xff0000) >> 16) * 100);
135 }
136 
137 static SENSOR_DEVICE_ATTR_RO(temp1_label, label, NSA320_TEMP);
138 static DEVICE_ATTR_RO(temp1_input);
139 static SENSOR_DEVICE_ATTR_RO(fan1_label, label, NSA320_FAN);
140 static DEVICE_ATTR_RO(fan1_input);
141 
142 static struct attribute *nsa320_attrs[] = {
143 	&sensor_dev_attr_temp1_label.dev_attr.attr,
144 	&dev_attr_temp1_input.attr,
145 	&sensor_dev_attr_fan1_label.dev_attr.attr,
146 	&dev_attr_fan1_input.attr,
147 	NULL
148 };
149 
150 ATTRIBUTE_GROUPS(nsa320);
151 
152 static const struct of_device_id of_nsa320_hwmon_match[] = {
153 	{ .compatible = "zyxel,nsa320-mcu", },
154 	{ },
155 };
156 
nsa320_hwmon_probe(struct platform_device * pdev)157 static int nsa320_hwmon_probe(struct platform_device *pdev)
158 {
159 	struct nsa320_hwmon	*hwmon;
160 	struct device		*classdev;
161 
162 	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
163 	if (!hwmon)
164 		return -ENOMEM;
165 
166 	/* Look up the GPIO pins to use */
167 	hwmon->act = devm_gpiod_get(&pdev->dev, "act", GPIOD_OUT_LOW);
168 	if (IS_ERR(hwmon->act))
169 		return PTR_ERR(hwmon->act);
170 
171 	hwmon->clk = devm_gpiod_get(&pdev->dev, "clk", GPIOD_OUT_HIGH);
172 	if (IS_ERR(hwmon->clk))
173 		return PTR_ERR(hwmon->clk);
174 
175 	hwmon->data = devm_gpiod_get(&pdev->dev, "data", GPIOD_IN);
176 	if (IS_ERR(hwmon->data))
177 		return PTR_ERR(hwmon->data);
178 
179 	mutex_init(&hwmon->update_lock);
180 
181 	classdev = devm_hwmon_device_register_with_groups(&pdev->dev,
182 					"nsa320", hwmon, nsa320_groups);
183 
184 	return PTR_ERR_OR_ZERO(classdev);
185 
186 }
187 
188 /* All allocations use devres so remove() is not needed. */
189 
190 static struct platform_driver nsa320_hwmon_driver = {
191 	.probe = nsa320_hwmon_probe,
192 	.driver = {
193 		.name = "nsa320-hwmon",
194 		.of_match_table = of_nsa320_hwmon_match,
195 	},
196 };
197 
198 module_platform_driver(nsa320_hwmon_driver);
199 
200 MODULE_DEVICE_TABLE(of, of_nsa320_hwmon_match);
201 MODULE_AUTHOR("Peter Schildmann <linux@schildmann.info>");
202 MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>");
203 MODULE_DESCRIPTION("NSA320 Hardware Monitoring");
204 MODULE_LICENSE("GPL v2");
205 MODULE_ALIAS("platform:nsa320-hwmon");
206