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/err.h> 11 #include <linux/hwmon.h> 12 #include <linux/module.h> 13 #include <linux/platform_device.h> 14 #include <linux/slab.h> 15 #include <linux/workqueue.h> 16 #include <soc/bcm2835/raspberrypi-firmware.h> 17 18 #define UNDERVOLTAGE_STICKY_BIT BIT(16) 19 20 struct rpi_hwmon_data { 21 struct device *hwmon_dev; 22 struct rpi_firmware *fw; 23 u32 last_throttled; 24 struct delayed_work get_values_poll_work; 25 }; 26 27 static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data) 28 { 29 u32 new_uv, old_uv, value; 30 int ret; 31 32 /* Request firmware to clear sticky bits */ 33 value = 0xffff; 34 35 ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED, 36 &value, sizeof(value)); 37 if (ret) { 38 dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n", 39 ret); 40 return; 41 } 42 43 new_uv = value & UNDERVOLTAGE_STICKY_BIT; 44 old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT; 45 data->last_throttled = value; 46 47 if (new_uv == old_uv) 48 return; 49 50 if (new_uv) 51 dev_crit(data->hwmon_dev, "Undervoltage detected!\n"); 52 else 53 dev_info(data->hwmon_dev, "Voltage normalised\n"); 54 55 sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm"); 56 } 57 58 static void get_values_poll(struct work_struct *work) 59 { 60 struct rpi_hwmon_data *data; 61 62 data = container_of(work, struct rpi_hwmon_data, 63 get_values_poll_work.work); 64 65 rpi_firmware_get_throttled(data); 66 67 /* 68 * We can't run faster than the sticky shift (100ms) since we get 69 * flipping in the sticky bits that are cleared. 70 */ 71 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ); 72 } 73 74 static int rpi_read(struct device *dev, enum hwmon_sensor_types type, 75 u32 attr, int channel, long *val) 76 { 77 struct rpi_hwmon_data *data = dev_get_drvdata(dev); 78 79 *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT); 80 return 0; 81 } 82 83 static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type, 84 u32 attr, int channel) 85 { 86 return 0444; 87 } 88 89 static const struct hwmon_channel_info *rpi_info[] = { 90 HWMON_CHANNEL_INFO(in, 91 HWMON_I_LCRIT_ALARM), 92 NULL 93 }; 94 95 static const struct hwmon_ops rpi_hwmon_ops = { 96 .is_visible = rpi_is_visible, 97 .read = rpi_read, 98 }; 99 100 static const struct hwmon_chip_info rpi_chip_info = { 101 .ops = &rpi_hwmon_ops, 102 .info = rpi_info, 103 }; 104 105 static int rpi_hwmon_probe(struct platform_device *pdev) 106 { 107 struct device *dev = &pdev->dev; 108 struct rpi_hwmon_data *data; 109 110 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 111 if (!data) 112 return -ENOMEM; 113 114 /* Parent driver assure that firmware is correct */ 115 data->fw = dev_get_drvdata(dev->parent); 116 117 data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt", 118 data, 119 &rpi_chip_info, 120 NULL); 121 122 INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll); 123 platform_set_drvdata(pdev, data); 124 125 if (!PTR_ERR_OR_ZERO(data->hwmon_dev)) 126 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ); 127 128 return PTR_ERR_OR_ZERO(data->hwmon_dev); 129 } 130 131 static int rpi_hwmon_remove(struct platform_device *pdev) 132 { 133 struct rpi_hwmon_data *data = platform_get_drvdata(pdev); 134 135 cancel_delayed_work_sync(&data->get_values_poll_work); 136 137 return 0; 138 } 139 140 static struct platform_driver rpi_hwmon_driver = { 141 .probe = rpi_hwmon_probe, 142 .remove = rpi_hwmon_remove, 143 .driver = { 144 .name = "raspberrypi-hwmon", 145 }, 146 }; 147 module_platform_driver(rpi_hwmon_driver); 148 149 MODULE_AUTHOR("Stefan Wahren <stefan.wahren@i2se.com>"); 150 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver"); 151 MODULE_LICENSE("GPL v2"); 152 MODULE_ALIAS("platform:raspberrypi-hwmon"); 153