[PATCH 4/4] ArmPkg/GenericWatchdogDxe: implement RegisterHandler() method

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Even though UEFI does not appear to use it, let's implement the
complete PI watchdog protocol, including handler registration,
which will be invoked instead of 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>
---
 ArmPkg/Drivers/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 717a180a64ec..21118a3c88d1 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);
+  } else {
+    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;
 }
 
 /**
-- 
2.17.1