From ba808d11f6a3206cbf4bee8340c7a26b2b19e809 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Tue, 18 Dec 2018 14:10:14 +0100
Subject: [PATCH 1/1] ArmPkg/GenericWatchdogDxe: implement RegisterHandler()
 method

Even though UEFI does not appear to use it, let's implement the
complete PI watchdog protocol, including handler registration,
which will be invoked before the ResetSystem() runtime service
when the watchdog timer expires.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
---
 .../GenericWatchdogDxe/GenericWatchdogDxe.c   | 34 ++++++++++++++-----
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
index 285727fc0e..a1ef0363eb 100644
--- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
+++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
@@ -42,6 +42,7 @@ STATIC UINTN mTimerFrequencyHz = 0;
 STATIC UINT64 mNumTimerTicks = 0;
 
 STATIC EFI_HARDWARE_INTERRUPT2_PROTOCOL *mInterruptProtocol;
+STATIC EFI_WATCHDOG_TIMER_NOTIFY        mWatchdogNotify;
 
 STATIC
 VOID
@@ -107,17 +108,25 @@ WatchdogInterruptHandler (
   )
 {
   STATIC CONST CHAR16 ResetString[]= L"The generic watchdog timer ran out.";
+  UINT64              TimerPeriod;
 
   WatchdogDisable ();
 
   mInterruptProtocol->EndOfInterrupt (mInterruptProtocol, Source);
 
-  gRT->ResetSystem (
-         EfiResetCold,
-         EFI_TIMEOUT,
-         StrSize (ResetString),
-         (VOID *) &ResetString
-         );
+  //
+  // The notify function should be called with the elapsed number of ticks
+  // since the watchdog was armed, which should exceed the timer period.
+  // We don't actually know the elapsed number of ticks, so let's return
+  // the timer period plus 1.
+  //
+  if (mWatchdogNotify != NULL) {
+    TimerPeriod = ((TIME_UNITS_PER_SECOND / mTimerFrequencyHz) * mNumTimerTicks);
+    mWatchdogNotify (TimerPeriod + 1);
+  }
+
+  gRT->ResetSystem (EfiResetCold, EFI_TIMEOUT, StrSize (ResetString),
+         (CHAR16 *)ResetString);
 
   // If we got here then the reset didn't work
   ASSERT (FALSE);
@@ -155,9 +164,16 @@ WatchdogRegisterHandler (
   IN EFI_WATCHDOG_TIMER_NOTIFY                NotifyFunction
   )
 {
-  // ERROR: This function is not supported.
-  // The watchdog will reset the board
-  return EFI_UNSUPPORTED;
+  if (mWatchdogNotify == NULL && NotifyFunction == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if (mWatchdogNotify != NULL && NotifyFunction != NULL) {
+    return EFI_ALREADY_STARTED;
+  }
+
+  mWatchdogNotify = NotifyFunction;
+  return EFI_SUCCESS;
 }
 
 /**
-- 
2.39.2