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
 21struct 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
 28static 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
 59static 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
 75static 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
 84static const struct hwmon_channel_info * const rpi_info[] = {
 85	HWMON_CHANNEL_INFO(in,
 86			   HWMON_I_LCRIT_ALARM),
 87	NULL
 88};
 89
 90static const struct hwmon_ops rpi_hwmon_ops = {
 91	.visible = 0444,
 92	.read = rpi_read,
 93};
 94
 95static const struct hwmon_chip_info rpi_chip_info = {
 96	.ops = &rpi_hwmon_ops,
 97	.info = rpi_info,
 98};
 99
100static 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
131static struct platform_driver rpi_hwmon_driver = {
132	.probe = rpi_hwmon_probe,
133	.driver = {
134		.name = "raspberrypi-hwmon",
135	},
136};
137module_platform_driver(rpi_hwmon_driver);
138
139MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
140MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
141MODULE_LICENSE("GPL v2");
142MODULE_ALIAS("platform:raspberrypi-hwmon");