cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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raspberrypi-hwmon.c (3603B)

      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 umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
     85			      u32 attr, int channel)
     86{
     87	return 0444;
     88}
     89
     90static const struct hwmon_channel_info *rpi_info[] = {
     91	HWMON_CHANNEL_INFO(in,
     92			   HWMON_I_LCRIT_ALARM),
     93	NULL
     94};
     95
     96static const struct hwmon_ops rpi_hwmon_ops = {
     97	.is_visible = rpi_is_visible,
     98	.read = rpi_read,
     99};
    100
    101static const struct hwmon_chip_info rpi_chip_info = {
    102	.ops = &rpi_hwmon_ops,
    103	.info = rpi_info,
    104};
    105
    106static 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, 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->parent);
    118
    119	data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
    120							       data,
    121							       &rpi_chip_info,
    122							       NULL);
    123	if (IS_ERR(data->hwmon_dev))
    124		return PTR_ERR(data->hwmon_dev);
    125
    126	ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
    127					   get_values_poll);
    128	if (ret)
    129		return ret;
    130	platform_set_drvdata(pdev, data);
    131
    132	schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
    133
    134	return 0;
    135}
    136
    137static struct platform_driver rpi_hwmon_driver = {
    138	.probe = rpi_hwmon_probe,
    139	.driver = {
    140		.name = "raspberrypi-hwmon",
    141	},
    142};
    143module_platform_driver(rpi_hwmon_driver);
    144
    145MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
    146MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
    147MODULE_LICENSE("GPL v2");
    148MODULE_ALIAS("platform:raspberrypi-hwmon");