[edk2-devel] [PATCH 5/6] UefiCpuPkg/LocalApicTimerDxe: warn if APIC Timer is used by other code

["Ni, Ray" <ray.ni@intel.com>]

LocalApicTimerDxe uses APIC Timer as the timer interrupt source.
Other code should not program the APIC Timer as it may cause the timer
interrupt be signaled at the incorrect timer period or the timer interrupt
might be disabled.

The patch prints warning debug messages in driver entrypoint when the
Initial Count is not the power-on default value 0.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
---
 UefiCpuPkg/LocalApicTimerDxe/LocalApicTimerDxe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/UefiCpuPkg/LocalApicTimerDxe/LocalApicTimerDxe.c b/UefiCpuPkg/LocalApicTimerDxe/LocalApicTimerDxe.c
index babf2476e3..14ab8fd03d 100644
--- a/UefiCpuPkg/LocalApicTimerDxe/LocalApicTimerDxe.c
+++ b/UefiCpuPkg/LocalApicTimerDxe/LocalApicTimerDxe.c
@@ -400,6 +400,15 @@ TimerDriverInitialize (
   //
   mTimerNotifyFunction = NULL;
 
+  if (GetApicTimerInitCount () != 0) {
+    DEBUG ((
+      DEBUG_WARN,
+      "Warning: APIC timer might be used by other drivers.\n"
+      "         The timer period may be changed unexpectedly.\n"
+      "         Please make sure no other code programs the APIC timer.\n"
+      ));
+  }
+
   //
   // Make sure the Timer Architectural Protocol is not already installed in the system
   //
-- 
2.39.1.windows.1



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