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/err.h>
11#include <linux/hwmon.h>
12#include <linux/module.h>
13#include <linux/platform_device.h>
14#include <linux/slab.h>
15#include <linux/workqueue.h>
16#include <soc/bcm2835/raspberrypi-firmware.h>
17
18#define UNDERVOLTAGE_STICKY_BIT BIT(16)
19
20struct rpi_hwmon_data {
21 struct device *hwmon_dev;
22 struct rpi_firmware *fw;
23 u32 last_throttled;
24 struct delayed_work get_values_poll_work;
25};
26
27static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
28{
29 u32 new_uv, old_uv, value;
30 int ret;
31
32 /* Request firmware to clear sticky bits */
33 value = 0xffff;
34
35 ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
36 &value, sizeof(value));
37 if (ret) {
38 dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
39 ret);
40 return;
41 }
42
43 new_uv = value & UNDERVOLTAGE_STICKY_BIT;
44 old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
45 data->last_throttled = value;
46
47 if (new_uv == old_uv)
48 return;
49
50 if (new_uv)
51 dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
52 else
53 dev_info(data->hwmon_dev, "Voltage normalised\n");
54
55 sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm");
56}
57
58static void get_values_poll(struct work_struct *work)
59{
60 struct rpi_hwmon_data *data;
61
62 data = container_of(work, struct rpi_hwmon_data,
63 get_values_poll_work.work);
64
65 rpi_firmware_get_throttled(data);
66
67 /*
68 * We can't run faster than the sticky shift (100ms) since we get
69 * flipping in the sticky bits that are cleared.
70 */
71 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
72}
73
74static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
75 u32 attr, int channel, long *val)
76{
77 struct rpi_hwmon_data *data = dev_get_drvdata(dev);
78
79 *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
80 return 0;
81}
82
83static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
84 u32 attr, int channel)
85{
86 return 0444;
87}
88
89static const u32 rpi_in_config[] = {
90 HWMON_I_LCRIT_ALARM,
91 0
92};
93
94static const struct hwmon_channel_info rpi_in = {
95 .type = hwmon_in,
96 .config = rpi_in_config,
97};
98
99static const struct hwmon_channel_info *rpi_info[] = {
100 &rpi_in,
101 NULL
102};
103
104static const struct hwmon_ops rpi_hwmon_ops = {
105 .is_visible = rpi_is_visible,
106 .read = rpi_read,
107};
108
109static const struct hwmon_chip_info rpi_chip_info = {
110 .ops = &rpi_hwmon_ops,
111 .info = rpi_info,
112};
113
114static int rpi_hwmon_probe(struct platform_device *pdev)
115{
116 struct device *dev = &pdev->dev;
117 struct rpi_hwmon_data *data;
118
119 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
120 if (!data)
121 return -ENOMEM;
122
123 /* Parent driver assure that firmware is correct */
124 data->fw = dev_get_drvdata(dev->parent);
125
126 data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
127 data,
128 &rpi_chip_info,
129 NULL);
130
131 INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
132 platform_set_drvdata(pdev, data);
133
134 if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
135 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
136
137 return PTR_ERR_OR_ZERO(data->hwmon_dev);
138}
139
140static int rpi_hwmon_remove(struct platform_device *pdev)
141{
142 struct rpi_hwmon_data *data = platform_get_drvdata(pdev);
143
144 cancel_delayed_work_sync(&data->get_values_poll_work);
145
146 return 0;
147}
148
149static struct platform_driver rpi_hwmon_driver = {
150 .probe = rpi_hwmon_probe,
151 .remove = rpi_hwmon_remove,
152 .driver = {
153 .name = "raspberrypi-hwmon",
154 },
155};
156module_platform_driver(rpi_hwmon_driver);
157
158MODULE_AUTHOR("Stefan Wahren <stefan.wahren@i2se.com>");
159MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
160MODULE_LICENSE("GPL v2");
161MODULE_ALIAS("platform:raspberrypi-hwmon");
162