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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