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 21 struct 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 28 static 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 59 static 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 75 static 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 84 static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type, 85 u32 attr, int channel) 86 { 87 return 0444; 88 } 89 90 static const struct hwmon_channel_info * const rpi_info[] = { 91 HWMON_CHANNEL_INFO(in, 92 HWMON_I_LCRIT_ALARM), 93 NULL 94 }; 95 96 static const struct hwmon_ops rpi_hwmon_ops = { 97 .is_visible = rpi_is_visible, 98 .read = rpi_read, 99 }; 100 101 static const struct hwmon_chip_info rpi_chip_info = { 102 .ops = &rpi_hwmon_ops, 103 .info = rpi_info, 104 }; 105 106 static 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 } 136 137 static struct platform_driver rpi_hwmon_driver = { 138 .probe = rpi_hwmon_probe, 139 .driver = { 140 .name = "raspberrypi-hwmon", 141 }, 142 }; 143 module_platform_driver(rpi_hwmon_driver); 144 145 MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>"); 146 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver"); 147 MODULE_LICENSE("GPL v2"); 148 MODULE_ALIAS("platform:raspberrypi-hwmon"); 149