UefiCpuPkg/CpuDxe: Put CPU to sleep during Idle events

When the MdeModulePkg gCoreEventIdleGuid event is signaled,
CpuSleep is called.  This will cause the CPU to sleep until
the next interrupt occurs.

Signed-off-by: jljusten
Reviewed-by: mdkinney
Reviewed-by: rsun3

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11842 6f19259b-4bc3-4df7-8a09-765794883524

UefiCpuPkg/CpuDxe/CpuDxe.c

@@ -1154,6 +1154,25 @@ InitInterruptDescriptorTable (
 }
 
 
+/**
+  Callback function for idle events.
+ 
+  @param  Event                 Event whose notification function is being invoked.
+  @param  Context               The pointer to the notification function's context,
+                                which is implementation-dependent.
+
+**/
+VOID
+EFIAPI
+IdleLoopEventCallback (
+  IN EFI_EVENT                Event,
+  IN VOID                     *Context
+  )
+{
+  CpuSleep ();
+}
+
+
 /**
   Initialize the state information for the CPU Architectural Protocol.
 
@@ -1173,6 +1192,7 @@ InitializeCpu (
   )
 {
   EFI_STATUS  Status;
+  EFI_EVENT   IdleLoopEvent;
 
   //
   // Make sure interrupts are disabled
@@ -1204,6 +1224,19 @@ InitializeCpu (
   //
   RefreshGcdMemoryAttributes ();
 
+  //
+  // Setup a callback for idle events
+  //
+  Status = gBS->CreateEventEx (
+                  EVT_NOTIFY_SIGNAL,
+                  TPL_NOTIFY,
+                  IdleLoopEventCallback,
+                  NULL,
+                  &gIdleLoopEventGuid,
+                  &IdleLoopEvent
+                  );
+  ASSERT_EFI_ERROR (Status);
+
   return Status;
 }