1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Copyright 2017 Google, Inc 4 */ 5 6 #ifndef _WDT_H_ 7 #define _WDT_H_ 8 9 /* 10 * Implement a simple watchdog uclass. Watchdog is basically a timer that 11 * is used to detect or recover from malfunction. During normal operation 12 * the watchdog would be regularly reset to prevent it from timing out. 13 * If, due to a hardware fault or program error, the computer fails to reset 14 * the watchdog, the timer will elapse and generate a timeout signal. 15 * The timeout signal is used to initiate corrective action or actions, 16 * which typically include placing the system in a safe, known state. 17 */ 18 19 /* 20 * Start the timer 21 * 22 * @dev: WDT Device 23 * @timeout_ms: Number of ticks (milliseconds) before timer expires 24 * @flags: Driver specific flags. This might be used to specify 25 * which action needs to be executed when the timer expires 26 * @return: 0 if OK, -ve on error 27 */ 28 int wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags); 29 30 /* 31 * Stop the timer, thus disabling the Watchdog. Use wdt_start to start it again. 32 * 33 * @dev: WDT Device 34 * @return: 0 if OK, -ve on error 35 */ 36 int wdt_stop(struct udevice *dev); 37 38 /* 39 * Reset the timer, typically restoring the counter to 40 * the value configured by start() 41 * 42 * @dev: WDT Device 43 * @return: 0 if OK, -ve on error 44 */ 45 int wdt_reset(struct udevice *dev); 46 47 /* 48 * Expire the timer, thus executing its action immediately. 49 * This is typically used to reset the board or peripherals. 50 * 51 * @dev: WDT Device 52 * @flags: Driver specific flags 53 * @return 0 if OK -ve on error. If wdt action is system reset, 54 * this function may never return. 55 */ 56 int wdt_expire_now(struct udevice *dev, ulong flags); 57 58 /* 59 * struct wdt_ops - Driver model wdt operations 60 * 61 * The uclass interface is implemented by all wdt devices which use 62 * driver model. 63 */ 64 struct wdt_ops { 65 /* 66 * Start the timer 67 * 68 * @dev: WDT Device 69 * @timeout_ms: Number of ticks (milliseconds) before the timer expires 70 * @flags: Driver specific flags. This might be used to specify 71 * which action needs to be executed when the timer expires 72 * @return: 0 if OK, -ve on error 73 */ 74 int (*start)(struct udevice *dev, u64 timeout_ms, ulong flags); 75 /* 76 * Stop the timer 77 * 78 * @dev: WDT Device 79 * @return: 0 if OK, -ve on error 80 */ 81 int (*stop)(struct udevice *dev); 82 /* 83 * Reset the timer, typically restoring the counter to 84 * the value configured by start() 85 * 86 * @dev: WDT Device 87 * @return: 0 if OK, -ve on error 88 */ 89 int (*reset)(struct udevice *dev); 90 /* 91 * Expire the timer, thus executing the action immediately (optional) 92 * 93 * If this function is not provided, a default implementation 94 * will be used, which sets the counter to 1 95 * and waits forever. This is good enough for system level 96 * reset, where the function is not expected to return, but might not be 97 * good enough for other use cases. 98 * 99 * @dev: WDT Device 100 * @flags: Driver specific flags 101 * @return 0 if OK -ve on error. May not return. 102 */ 103 int (*expire_now)(struct udevice *dev, ulong flags); 104 }; 105 106 #endif /* _WDT_H_ */ 107