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(fw: data->fw, tag: RPI_FIRMWARE_GET_THROTTLED, |
37 | data: &value, len: 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(dev: data->hwmon_dev, type: hwmon_in, attr: hwmon_in_lcrit_alarm, channel: 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(dwork: &data->get_values_poll_work, delay: 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 umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type, |
85 | u32 attr, int channel) |
86 | { |
87 | return 0444; |
88 | } |
89 | |
90 | static const struct hwmon_channel_info * const rpi_info[] = { |
91 | HWMON_CHANNEL_INFO(in, |
92 | HWMON_I_LCRIT_ALARM), |
93 | NULL |
94 | }; |
95 | |
96 | static const struct hwmon_ops rpi_hwmon_ops = { |
97 | .is_visible = rpi_is_visible, |
98 | .read = rpi_read, |
99 | }; |
100 | |
101 | static const struct hwmon_chip_info rpi_chip_info = { |
102 | .ops = &rpi_hwmon_ops, |
103 | .info = rpi_info, |
104 | }; |
105 | |
106 | static int rpi_hwmon_probe(struct platform_device *pdev) |
107 | { |
108 | struct device *dev = &pdev->dev; |
109 | struct rpi_hwmon_data *data; |
110 | int ret; |
111 | |
112 | data = devm_kzalloc(dev, size: sizeof(*data), GFP_KERNEL); |
113 | if (!data) |
114 | return -ENOMEM; |
115 | |
116 | /* Parent driver assure that firmware is correct */ |
117 | data->fw = dev_get_drvdata(dev: dev->parent); |
118 | |
119 | data->hwmon_dev = devm_hwmon_device_register_with_info(dev, name: "rpi_volt" , |
120 | drvdata: data, |
121 | info: &rpi_chip_info, |
122 | NULL); |
123 | if (IS_ERR(ptr: data->hwmon_dev)) |
124 | return PTR_ERR(ptr: data->hwmon_dev); |
125 | |
126 | ret = devm_delayed_work_autocancel(dev, w: &data->get_values_poll_work, |
127 | worker: get_values_poll); |
128 | if (ret) |
129 | return ret; |
130 | platform_set_drvdata(pdev, data); |
131 | |
132 | schedule_delayed_work(dwork: &data->get_values_poll_work, delay: 2 * HZ); |
133 | |
134 | return 0; |
135 | } |
136 | |
137 | static struct platform_driver rpi_hwmon_driver = { |
138 | .probe = rpi_hwmon_probe, |
139 | .driver = { |
140 | .name = "raspberrypi-hwmon" , |
141 | }, |
142 | }; |
143 | module_platform_driver(rpi_hwmon_driver); |
144 | |
145 | MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>" ); |
146 | MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver" ); |
147 | MODULE_LICENSE("GPL v2" ); |
148 | MODULE_ALIAS("platform:raspberrypi-hwmon" ); |
149 | |