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 struct udevice; 10 11 /* 12 * Implement a simple watchdog uclass. Watchdog is basically a timer that 13 * is used to detect or recover from malfunction. During normal operation 14 * the watchdog would be regularly reset to prevent it from timing out. 15 * If, due to a hardware fault or program error, the computer fails to reset 16 * the watchdog, the timer will elapse and generate a timeout signal. 17 * The timeout signal is used to initiate corrective action or actions, 18 * which typically include placing the system in a safe, known state. 19 */ 20 21 /* 22 * Start the timer 23 * 24 * @dev: WDT Device 25 * @timeout_ms: Number of ticks (milliseconds) before timer expires 26 * @flags: Driver specific flags. This might be used to specify 27 * which action needs to be executed when the timer expires 28 * @return: 0 if OK, -ve on error 29 */ 30 int wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags); 31 32 /* 33 * Stop the timer, thus disabling the Watchdog. Use wdt_start to start it again. 34 * 35 * @dev: WDT Device 36 * @return: 0 if OK, -ve on error 37 */ 38 int wdt_stop(struct udevice *dev); 39 40 /* 41 * Reset the timer, typically restoring the counter to 42 * the value configured by start() 43 * 44 * @dev: WDT Device 45 * @return: 0 if OK, -ve on error 46 */ 47 int wdt_reset(struct udevice *dev); 48 49 /* 50 * Expire the timer, thus executing its action immediately. 51 * This is typically used to reset the board or peripherals. 52 * 53 * @dev: WDT Device 54 * @flags: Driver specific flags 55 * @return 0 if OK -ve on error. If wdt action is system reset, 56 * this function may never return. 57 */ 58 int wdt_expire_now(struct udevice *dev, ulong flags); 59 60 /* 61 * struct wdt_ops - Driver model wdt operations 62 * 63 * The uclass interface is implemented by all wdt devices which use 64 * driver model. 65 */ 66 struct wdt_ops { 67 /* 68 * Start the timer 69 * 70 * @dev: WDT Device 71 * @timeout_ms: Number of ticks (milliseconds) before the timer expires 72 * @flags: Driver specific flags. This might be used to specify 73 * which action needs to be executed when the timer expires 74 * @return: 0 if OK, -ve on error 75 */ 76 int (*start)(struct udevice *dev, u64 timeout_ms, ulong flags); 77 /* 78 * Stop the timer 79 * 80 * @dev: WDT Device 81 * @return: 0 if OK, -ve on error 82 */ 83 int (*stop)(struct udevice *dev); 84 /* 85 * Reset the timer, typically restoring the counter to 86 * the value configured by start() 87 * 88 * @dev: WDT Device 89 * @return: 0 if OK, -ve on error 90 */ 91 int (*reset)(struct udevice *dev); 92 /* 93 * Expire the timer, thus executing the action immediately (optional) 94 * 95 * If this function is not provided, a default implementation 96 * will be used, which sets the counter to 1 97 * and waits forever. This is good enough for system level 98 * reset, where the function is not expected to return, but might not be 99 * good enough for other use cases. 100 * 101 * @dev: WDT Device 102 * @flags: Driver specific flags 103 * @return 0 if OK -ve on error. May not return. 104 */ 105 int (*expire_now)(struct udevice *dev, ulong flags); 106 }; 107 108 int initr_watchdog(void); 109 110 #endif /* _WDT_H_ */ 111