ArmPkg/TimerDxe: Fixed real time period

Prior to this change, the TimerPeriod was re-initialize at the
end of the interrupt handling with the value of the period.
It means the real timer period was: Timer Interrupt Processing
time + Timer Period

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15923 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 50 insertions, 8 deletions

diff --git a/ArmPkg/Drivers/TimerDxe/TimerDxe.c b/ArmPkg/Drivers/TimerDxe/TimerDxe.c
index 279b50f290..329b085ec4 100644
--- a/ArmPkg/Drivers/TimerDxe/TimerDxe.c
+++ b/ArmPkg/Drivers/TimerDxe/TimerDxe.c
@@ -35,6 +35,10 @@ EFI_EVENT             EfiExitBootServicesEvent = (EFI_EVENT)NULL;
 

 // The current period of the timer interrupt

 UINT64 mTimerPeriod = 0;

+// The latest Timer Tick calculated for mTimerPeriod

+UINT64 mTimerTicks = 0;

+// Number of elapsed period since the last Timer interrupt

+UINT64 mElapsedPeriod = 1;

 

 // Cached copy of the Hardware Interrupt protocol instance

 EFI_HARDWARE_INTERRUPT_PROTOCOL *gInterrupt = NULL;

@@ -135,26 +139,44 @@ TimerDriverSetTimerPeriod (
   IN UINT64                   TimerPeriod

   )

 {

+  UINT64      CounterValue;

   UINT64      TimerTicks;

+  EFI_TPL     OriginalTPL;

 

   // Always disable the timer

   ArmArchTimerDisableTimer ();

 

   if (TimerPeriod != 0) {

-    // TimerTicks = TimerPeriod in 1ms unit x Frequency.10^-3

-    //            = TimerPeriod.10^-4 x Frequency.10^-3

-    //            = (TimerPeriod x Frequency) x 10^-7

+    // mTimerTicks = TimerPeriod in 1ms unit x Frequency.10^-3

+    //             = TimerPeriod.10^-4 x Frequency.10^-3

+    //             = (TimerPeriod x Frequency) x 10^-7

     TimerTicks = MultU64x32 (TimerPeriod, FixedPcdGet32 (PcdArmArchTimerFreqInHz));

     TimerTicks = DivU64x32 (TimerTicks, 10000000U);

 

-    ArmArchTimerSetTimerVal ((UINTN)TimerTicks);

+    // Raise TPL to update the mTimerTicks and mTimerPeriod to ensure these values

+    // are coherent in the interrupt handler

+    OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);

+

+    mTimerTicks    = TimerTicks;

+    mTimerPeriod   = TimerPeriod;

+    mElapsedPeriod = 1;

+

+    gBS->RestoreTPL (OriginalTPL);

+

+    // Get value of the current physical timer

+    CounterValue = ArmReadCntPct ();

+    // Set the interrupt in Current Time + mTimerTick

+    ArmWriteCntpCval (CounterValue + mTimerTicks);

 

     // Enable the timer

     ArmArchTimerEnableTimer ();

+  } else {

+    // Save the new timer period

+    mTimerPeriod   = TimerPeriod;

+    // Reset the elapsed period

+    mElapsedPeriod = 1;

   }

 

-  // Save the new timer period

-  mTimerPeriod = TimerPeriod;

   return EFI_SUCCESS;

 }

 

@@ -274,6 +296,8 @@ TimerInterruptHandler (
   )

 {

   EFI_TPL      OriginalTPL;

+  UINT64       CurrentValue;

+  UINT64       CompareValue;

 

   //

   // DXE core uses this callback for the EFI timer tick. The DXE core uses locks

@@ -289,11 +313,29 @@ TimerInterruptHandler (
     gInterrupt->EndOfInterrupt (gInterrupt, Source);

 

     if (mTimerNotifyFunction) {

-      mTimerNotifyFunction (mTimerPeriod);

+      mTimerNotifyFunction (mTimerPeriod * mElapsedPeriod);

     }

 

+    //

     // Reload the Timer

-    TimerDriverSetTimerPeriod (&gTimer, mTimerPeriod);

+    //

+

+    // Get current counter value

+    CurrentValue = ArmReadCntPct ();

+    // Get the counter value to compare with

+    CompareValue = ArmReadCntpCval ();

+

+    // This loop is needed in case we missed interrupts (eg: case when the interrupt handling

+    // has taken longer than mTickPeriod).

+    // Note: Physical Counter is counting up

+    mElapsedPeriod = 0;

+    do {

+      CompareValue += mTimerTicks;

+      mElapsedPeriod++;

+    } while (CompareValue < CurrentValue);

+

+    // Set next compare value

+    ArmWriteCntpCval (CompareValue);

   }

 

   // Enable timer interrupts