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// SPDX-License-Identifier: GPL-2.0+
/*
* Raspberry Pi voltage sensor driver
*
* Based on firmware/raspberrypi.c by Noralf Trønnes
*
* Copyright (C) 2018 Stefan Wahren <stefan.wahren@i2se.com>
*/
#include <linux/device.h>
#include <linux/devm-helpers.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <soc/bcm2835/raspberrypi-firmware.h>
#define UNDERVOLTAGE_STICKY_BIT BIT(16)
struct rpi_hwmon_data {
struct device *hwmon_dev;
struct rpi_firmware *fw;
u32 last_throttled;
struct delayed_work get_values_poll_work;
};
static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
{
u32 new_uv, old_uv, value;
int ret;
/* Request firmware to clear sticky bits */
value = 0xffff;
ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
&value, sizeof(value));
if (ret) {
dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
ret);
return;
}
new_uv = value & UNDERVOLTAGE_STICKY_BIT;
old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
data->last_throttled = value;
if (new_uv == old_uv)
return;
if (new_uv)
dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
else
dev_info(data->hwmon_dev, "Voltage normalised\n");
hwmon_notify_event(data->hwmon_dev, hwmon_in, hwmon_in_lcrit_alarm, 0);
}
static void get_values_poll(struct work_struct *work)
{
struct rpi_hwmon_data *data;
data = container_of(work, struct rpi_hwmon_data,
get_values_poll_work.work);
rpi_firmware_get_throttled(data);
/*
* We can't run faster than the sticky shift (100ms) since we get
* flipping in the sticky bits that are cleared.
*/
schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
}
static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long *val)
{
struct rpi_hwmon_data *data = dev_get_drvdata(dev);
*val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
return 0;
}
static const struct hwmon_channel_info * const rpi_info[] = {
HWMON_CHANNEL_INFO(in,
HWMON_I_LCRIT_ALARM),
NULL
};
static const struct hwmon_ops rpi_hwmon_ops = {
.visible = 0444,
.read = rpi_read,
};
static const struct hwmon_chip_info rpi_chip_info = {
.ops = &rpi_hwmon_ops,
.info = rpi_info,
};
static int rpi_hwmon_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct rpi_hwmon_data *data;
int ret;
data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
/* Parent driver assure that firmware is correct */
data->fw = dev_get_drvdata(dev->parent);
data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
data,
&rpi_chip_info,
NULL);
if (IS_ERR(data->hwmon_dev))
return PTR_ERR(data->hwmon_dev);
ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
get_values_poll);
if (ret)
return ret;
platform_set_drvdata(pdev, data);
schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
return 0;
}
static struct platform_driver rpi_hwmon_driver = {
.probe = rpi_hwmon_probe,
.driver = {
.name = "raspberrypi-hwmon",
},
};
module_platform_driver(rpi_hwmon_driver);
MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:raspberrypi-hwmon");
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