1 /* 2 * Copyright 2017 Google, Inc 3 * 4 * SPDX-License-Identifier: GPL-2.0+ 5 */ 6 7 #ifndef _WDT_H_ 8 #define _WDT_H_ 9 10 /* 11 * Implement a simple watchdog uclass. Watchdog is basically a timer that 12 * is used to detect or recover from malfunction. During normal operation 13 * the watchdog would be regularly reset to prevent it from timing out. 14 * If, due to a hardware fault or program error, the computer fails to reset 15 * the watchdog, the timer will elapse and generate a timeout signal. 16 * The timeout signal is used to initiate corrective action or actions, 17 * which typically include placing the system in a safe, known state. 18 */ 19 20 /* 21 * Start the timer 22 * 23 * @dev: WDT Device 24 * @timeout: Number of ticks before timer expires 25 * @flags: Driver specific flags. This might be used to specify 26 * which action needs to be executed when the timer expires 27 * @return: 0 if OK, -ve on error 28 */ 29 int wdt_start(struct udevice *dev, u64 timeout, ulong flags); 30 31 /* 32 * Stop the timer, thus disabling the Watchdog. Use wdt_start to start it again. 33 * 34 * @dev: WDT Device 35 * @return: 0 if OK, -ve on error 36 */ 37 int wdt_stop(struct udevice *dev); 38 39 /* 40 * Reset the timer, typically restoring the counter to 41 * the value configured by start() 42 * 43 * @dev: WDT Device 44 * @return: 0 if OK, -ve on error 45 */ 46 int wdt_reset(struct udevice *dev); 47 48 /* 49 * Expire the timer, thus executing its action immediately. 50 * This is typically used to reset the board or peripherals. 51 * 52 * @dev: WDT Device 53 * @flags: Driver specific flags 54 * @return 0 if OK -ve on error. If wdt action is system reset, 55 * this function may never return. 56 */ 57 int wdt_expire_now(struct udevice *dev, ulong flags); 58 59 /* 60 * struct wdt_ops - Driver model wdt operations 61 * 62 * The uclass interface is implemented by all wdt devices which use 63 * driver model. 64 */ 65 struct wdt_ops { 66 /* 67 * Start the timer 68 * 69 * @dev: WDT Device 70 * @timeout: Number of ticks before the timer expires 71 * @flags: Driver specific flags. This might be used to specify 72 * which action needs to be executed when the timer expires 73 * @return: 0 if OK, -ve on error 74 */ 75 int (*start)(struct udevice *dev, u64 timeout, ulong flags); 76 /* 77 * Stop the timer 78 * 79 * @dev: WDT Device 80 * @return: 0 if OK, -ve on error 81 */ 82 int (*stop)(struct udevice *dev); 83 /* 84 * Reset the timer, typically restoring the counter to 85 * the value configured by start() 86 * 87 * @dev: WDT Device 88 * @return: 0 if OK, -ve on error 89 */ 90 int (*reset)(struct udevice *dev); 91 /* 92 * Expire the timer, thus executing the action immediately (optional) 93 * 94 * If this function is not provided, a default implementation 95 * will be used, which sets the counter to 1 96 * and waits forever. This is good enough for system level 97 * reset, where the function is not expected to return, but might not be 98 * good enough for other use cases. 99 * 100 * @dev: WDT Device 101 * @flags: Driver specific flags 102 * @return 0 if OK -ve on error. May not return. 103 */ 104 int (*expire_now)(struct udevice *dev, ulong flags); 105 }; 106 107 #endif /* _WDT_H_ */ 108