u-boot/include/wdt.h
maxims@google.com 0753bc2d30 dm: Simple Watchdog uclass
This is a simple uclass for Watchdog Timers. It has four operations:
start, restart, reset, stop. Drivers must implement start, restart and
stop operations, while implementing reset is optional: It's default
implementation expires watchdog timer in one clock tick.

Signed-off-by: Maxim Sloyko <maxims@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2017-05-08 11:57:30 -04:00

107 lines
3 KiB
C

/*
* Copyright 2017 Google, Inc
*
* SPDX-License-Identifier: GPL-2.0+
*/
#ifndef _WDT_H_
#define _WDT_H_
/*
* Implement a simple watchdog uclass. Watchdog is basically a timer that
* is used to detect or recover from malfunction. During normal operation
* the watchdog would be regularly reset to prevent it from timing out.
* If, due to a hardware fault or program error, the computer fails to reset
* the watchdog, the timer will elapse and generate a timeout signal.
* The timeout signal is used to initiate corrective action or actions,
* which typically include placing the system in a safe, known state.
*/
/*
* Start the timer
*
* @dev: WDT Device
* @timeout: Number of ticks before timer expires
* @flags: Driver specific flags. This might be used to specify
* which action needs to be executed when the timer expires
* @return: 0 if OK, -ve on error
*/
int wdt_start(struct udevice *dev, u64 timeout, ulong flags);
/*
* Stop the timer, thus disabling the Watchdog. Use wdt_start to start it again.
*
* @dev: WDT Device
* @return: 0 if OK, -ve on error
*/
int wdt_stop(struct udevice *dev);
/*
* Reset the timer, typically restoring the counter to
* the value configured by start()
*
* @dev: WDT Device
* @return: 0 if OK, -ve on error
*/
int wdt_reset(struct udevice *dev);
/*
* Expire the timer, thus executing its action immediately.
* This is typically used to reset the board or peripherals.
*
* @dev: WDT Device
* @flags: Driver specific flags
* @return 0 if OK -ve on error. If wdt action is system reset,
* this function may never return.
*/
int wdt_expire_now(struct udevice *dev, ulong flags);
/*
* struct wdt_ops - Driver model wdt operations
*
* The uclass interface is implemented by all wdt devices which use
* driver model.
*/
struct wdt_ops {
/*
* Start the timer
*
* @dev: WDT Device
* @timeout: Number of ticks before the timer expires
* @flags: Driver specific flags. This might be used to specify
* which action needs to be executed when the timer expires
* @return: 0 if OK, -ve on error
*/
int (*start)(struct udevice *dev, u64 timeout, ulong flags);
/*
* Stop the timer
*
* @dev: WDT Device
* @return: 0 if OK, -ve on error
*/
int (*stop)(struct udevice *dev);
/*
* Reset the timer, typically restoring the counter to
* the value configured by start()
*
* @dev: WDT Device
* @return: 0 if OK, -ve on error
*/
int (*reset)(struct udevice *dev);
/*
* Expire the timer, thus executing the action immediately (optional)
*
* If this function is not provided, a default implementation
* will be used, which sets the counter to 1
* and waits forever. This is good enough for system level
* reset, where the function is not expected to return, but might not be
* good enough for other use cases.
*
* @dev: WDT Device
* @flags: Driver specific flags
* @return 0 if OK -ve on error. May not return.
*/
int (*expire_now)(struct udevice *dev, ulong flags);
};
#endif /* _WDT_H_ */