1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Copyright 2017 Google, Inc
4 */
5
6#ifndef _WDT_H_
7#define _WDT_H_
8
9struct 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 */
30int 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 */
38int wdt_stop(struct udevice *dev);
39
40/*
41 * Stop all registered watchdog devices.
42 *
43 * @return: 0 if ok, first error encountered otherwise (but wdt_stop()
44 * is still called on following devices)
45 */
46int wdt_stop_all(void);
47
48/*
49 * Reset the timer, typically restoring the counter to
50 * the value configured by start()
51 *
52 * @dev: WDT Device
53 * @return: 0 if OK, -ve on error
54 */
55int wdt_reset(struct udevice *dev);
56
57/*
58 * Expire the timer, thus executing its action immediately.
59 * This is typically used to reset the board or peripherals.
60 *
61 * @dev: WDT Device
62 * @flags: Driver specific flags
63 * Return: 0 if OK -ve on error. If wdt action is system reset,
64 * this function may never return.
65 */
66int wdt_expire_now(struct udevice *dev, ulong flags);
67
68/*
69 * struct wdt_ops - Driver model wdt operations
70 *
71 * The uclass interface is implemented by all wdt devices which use
72 * driver model.
73 */
74struct wdt_ops {
75	/*
76	 * Start the timer
77	 *
78	 * @dev: WDT Device
79	 * @timeout_ms: Number of ticks (milliseconds) before the timer expires
80	 * @flags: Driver specific flags. This might be used to specify
81	 * which action needs to be executed when the timer expires
82	 * @return: 0 if OK, -ve on error
83	 */
84	int (*start)(struct udevice *dev, u64 timeout_ms, ulong flags);
85	/*
86	 * Stop the timer
87	 *
88	 * @dev: WDT Device
89	 * @return: 0 if OK, -ve on error
90	 */
91	int (*stop)(struct udevice *dev);
92	/*
93	 * Reset the timer, typically restoring the counter to
94	 * the value configured by start()
95	 *
96	 * @dev: WDT Device
97	 * @return: 0 if OK, -ve on error
98	 */
99	int (*reset)(struct udevice *dev);
100	/*
101	 * Expire the timer, thus executing the action immediately (optional)
102	 *
103	 * If this function is not provided, a default implementation
104	 * will be used, which sets the counter to 1
105	 * and waits forever. This is good enough for system level
106	 * reset, where the function is not expected to return, but might not be
107	 * good enough for other use cases.
108	 *
109	 * @dev: WDT Device
110	 * @flags: Driver specific flags
111	 * @return 0 if OK -ve on error. May not return.
112	 */
113	int (*expire_now)(struct udevice *dev, ulong flags);
114};
115
116int initr_watchdog(void);
117
118#endif  /* _WDT_H_ */
119