xref: /linux/drivers/hwmon/raspberrypi-hwmon.c (revision 7f71507851fc7764b36a3221839607d3a45c2025)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Raspberry Pi voltage sensor driver
4  *
5  * Based on firmware/raspberrypi.c by Noralf Trønnes
6  *
7  * Copyright (C) 2018 Stefan Wahren <stefan.wahren@i2se.com>
8  */
9 #include <linux/device.h>
10 #include <linux/devm-helpers.h>
11 #include <linux/err.h>
12 #include <linux/hwmon.h>
13 #include <linux/module.h>
14 #include <linux/platform_device.h>
15 #include <linux/slab.h>
16 #include <linux/workqueue.h>
17 #include <soc/bcm2835/raspberrypi-firmware.h>
18 
19 #define UNDERVOLTAGE_STICKY_BIT	BIT(16)
20 
21 struct rpi_hwmon_data {
22 	struct device *hwmon_dev;
23 	struct rpi_firmware *fw;
24 	u32 last_throttled;
25 	struct delayed_work get_values_poll_work;
26 };
27 
28 static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
29 {
30 	u32 new_uv, old_uv, value;
31 	int ret;
32 
33 	/* Request firmware to clear sticky bits */
34 	value = 0xffff;
35 
36 	ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
37 				    &value, sizeof(value));
38 	if (ret) {
39 		dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
40 			     ret);
41 		return;
42 	}
43 
44 	new_uv = value & UNDERVOLTAGE_STICKY_BIT;
45 	old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
46 	data->last_throttled = value;
47 
48 	if (new_uv == old_uv)
49 		return;
50 
51 	if (new_uv)
52 		dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
53 	else
54 		dev_info(data->hwmon_dev, "Voltage normalised\n");
55 
56 	hwmon_notify_event(data->hwmon_dev, hwmon_in, hwmon_in_lcrit_alarm, 0);
57 }
58 
59 static void get_values_poll(struct work_struct *work)
60 {
61 	struct rpi_hwmon_data *data;
62 
63 	data = container_of(work, struct rpi_hwmon_data,
64 			    get_values_poll_work.work);
65 
66 	rpi_firmware_get_throttled(data);
67 
68 	/*
69 	 * We can't run faster than the sticky shift (100ms) since we get
70 	 * flipping in the sticky bits that are cleared.
71 	 */
72 	schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
73 }
74 
75 static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
76 		    u32 attr, int channel, long *val)
77 {
78 	struct rpi_hwmon_data *data = dev_get_drvdata(dev);
79 
80 	*val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
81 	return 0;
82 }
83 
84 static const struct hwmon_channel_info * const rpi_info[] = {
85 	HWMON_CHANNEL_INFO(in,
86 			   HWMON_I_LCRIT_ALARM),
87 	NULL
88 };
89 
90 static const struct hwmon_ops rpi_hwmon_ops = {
91 	.visible = 0444,
92 	.read = rpi_read,
93 };
94 
95 static const struct hwmon_chip_info rpi_chip_info = {
96 	.ops = &rpi_hwmon_ops,
97 	.info = rpi_info,
98 };
99 
100 static int rpi_hwmon_probe(struct platform_device *pdev)
101 {
102 	struct device *dev = &pdev->dev;
103 	struct rpi_hwmon_data *data;
104 	int ret;
105 
106 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
107 	if (!data)
108 		return -ENOMEM;
109 
110 	/* Parent driver assure that firmware is correct */
111 	data->fw = dev_get_drvdata(dev->parent);
112 
113 	data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
114 							       data,
115 							       &rpi_chip_info,
116 							       NULL);
117 	if (IS_ERR(data->hwmon_dev))
118 		return PTR_ERR(data->hwmon_dev);
119 
120 	ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
121 					   get_values_poll);
122 	if (ret)
123 		return ret;
124 	platform_set_drvdata(pdev, data);
125 
126 	schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
127 
128 	return 0;
129 }
130 
131 static struct platform_driver rpi_hwmon_driver = {
132 	.probe = rpi_hwmon_probe,
133 	.driver = {
134 		.name = "raspberrypi-hwmon",
135 	},
136 };
137 module_platform_driver(rpi_hwmon_driver);
138 
139 MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
140 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
141 MODULE_LICENSE("GPL v2");
142 MODULE_ALIAS("platform:raspberrypi-hwmon");
143