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