update comments

[mirror_edk2.git] / EmbeddedPkg / TemplateTimerDxe / Timer.c

diff --git a/EmbeddedPkg/TemplateTimerDxe/Timer.c b/EmbeddedPkg/TemplateTimerDxe/Timer.c
index 4bfa3e862278b929aa2c762c06bb38b7247e75d0..a48d4b52ebaea81c7bbdb78ed6dab14bae983153 100644 (file)
--- a/EmbeddedPkg/TemplateTimerDxe/Timer.c
+++ b/EmbeddedPkg/TemplateTimerDxe/Timer.c
@@ -72,7 +72,11 @@ TimerInterruptHandler (
 {\r
        EFI_TPL                                                 OriginalTPL;\r
 \r
-  // Mask all interrupts\r
+  //\r
+  // DXE core uses this callback for the EFI timer tick. The DXE core uses locks \r
+  // that raise to TPL_HIGH and then restore back to current level. Thus we need\r
+  // to make sure TPL level is set to TPL_HIGH while we are handling the timer tick. \r
+  //\r
        OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
 \r
   MmioWrite32 (TIMER_CMD, 0);\r