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1// SPDX-License-Identifier: GPL-2.0+2/*3 * Raspberry Pi voltage sensor driver4 *5 * Based on firmware/raspberrypi.c by Noralf Trønnes6 *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 else54 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 get70 * 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 * const rpi_info[] = {91 HWMON_CHANNEL_INFO(in,92 HWMON_I_LCRIT_ALARM),93 NULL94};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");149