include/wdt.h

   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  * 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  */
  46 int 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  */
  55 int 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  */
  66 int 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  */
  74 struct 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
 116 int initr_watchdog(void);
 117
 118 #endif  /* _WDT_H_ */