hwmon: Add support for RPi voltage sensor (74d1e007) · Commits · e / devices / android_kernel_fairphone_FP4

Documentation/hwmon/raspberrypi-hwmon

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		Kernel driver raspberrypi-hwmon
		===============================

		Supported boards:
		* Raspberry Pi A+ (via GPIO on SoC)
		* Raspberry Pi B+ (via GPIO on SoC)
		* Raspberry Pi 2 B (via GPIO on SoC)
		* Raspberry Pi 3 B (via GPIO on port expander)
		* Raspberry Pi 3 B+ (via PMIC)

		Author: Stefan Wahren <stefan.wahren@i2se.com>

		Description
		-----------

		This driver periodically polls a mailbox property of the VC4 firmware to detect
		undervoltage conditions.

		Sysfs entries
		-------------

		in0_lcrit_alarm Undervoltage alarm

drivers/hwmon/Kconfig

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		@@ -1298,6 +1298,16 @@ config SENSORS_PWM_FAN
		This driver can also be built as a module. If so, the module
		will be called pwm-fan.

		config SENSORS_RASPBERRYPI_HWMON
		tristate "Raspberry Pi voltage monitor"
		depends on RASPBERRYPI_FIRMWARE \|\| (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
		help
		If you say yes here you get support for voltage sensor on the
		Raspberry Pi.

		This driver can also be built as a module. If so, the module
		will be called raspberrypi-hwmon.

		config SENSORS_SHT15
		tristate "Sensiron humidity and temperature sensors. SHT15 and compat."
		depends on GPIOLIB \|\| COMPILE_TEST

drivers/hwmon/Makefile

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		@@ -141,6 +141,7 @@ obj-$(CONFIG_SENSORS_PC87427) += pc87427.o
		obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o
		obj-$(CONFIG_SENSORS_POWR1220) += powr1220.o
		obj-$(CONFIG_SENSORS_PWM_FAN) += pwm-fan.o
		obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON) += raspberrypi-hwmon.o
		obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o
		obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
		obj-$(CONFIG_SENSORS_SCH5627) += sch5627.o

drivers/hwmon/raspberrypi-hwmon.c

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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/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");

		sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm");
		}

		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 umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
		u32 attr, int channel)
		{
		return 0444;
		}

		static const u32 rpi_in_config[] = {
		HWMON_I_LCRIT_ALARM,
		0
		};

		static const struct hwmon_channel_info rpi_in = {
		.type = hwmon_in,
		.config = rpi_in_config,
		};

		static const struct hwmon_channel_info *rpi_info[] = {
		&rpi_in,
		NULL
		};

		static const struct hwmon_ops rpi_hwmon_ops = {
		.is_visible = rpi_is_visible,
		.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);

		/* Init throttled */
		ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
		&data->last_throttled,
		sizeof(data->last_throttled));

		data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
		data,
		&rpi_chip_info,
		NULL);

		INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
		platform_set_drvdata(pdev, data);

		if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
		schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);

		return PTR_ERR_OR_ZERO(data->hwmon_dev);
		}

		static int rpi_hwmon_remove(struct platform_device *pdev)
		{
		struct rpi_hwmon_data *data = platform_get_drvdata(pdev);

		cancel_delayed_work_sync(&data->get_values_poll_work);

		return 0;
		}

		static struct platform_driver rpi_hwmon_driver = {
		.probe = rpi_hwmon_probe,
		.remove = rpi_hwmon_remove,
		.driver = {
		.name = "raspberrypi-hwmon",
		},
		};
		module_platform_driver(rpi_hwmon_driver);

		MODULE_AUTHOR("Stefan Wahren <stefan.wahren@i2se.com>");
		MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
		MODULE_LICENSE("GPL v2");