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