diff options
| -rw-r--r-- | ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c b/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c index 76f94c9..cc1be01 100644 --- a/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c +++ b/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c @@ -62,6 +62,8 @@ MicroSecondDelay ( {
UINT64 TimerTicks64;
UINT64 SystemCounterVal;
+ UINT64 PreviousSystemCounterVal;
+ UINT64 DeltaCounterVal;
// Calculate counter ticks that represent requested delay:
// = MicroSeconds x TICKS_PER_MICRO_SEC
@@ -75,13 +77,17 @@ MicroSecondDelay ( );
// Read System Counter value
- SystemCounterVal = ArmGenericTimerGetSystemCount ();
-
- TimerTicks64 += SystemCounterVal;
+ PreviousSystemCounterVal = ArmGenericTimerGetSystemCount ();
// Wait until delay count expires.
- while (SystemCounterVal < TimerTicks64) {
+ while (TimerTicks64 > 0) {
SystemCounterVal = ArmGenericTimerGetSystemCount ();
+ // Get how much we advanced this tick. Wrap around still has delta correct
+ DeltaCounterVal = (SystemCounterVal - PreviousSystemCounterVal)
+ & (MAX_UINT64 >> 8); // Account for a lesser (minimum) size
+ // Never wrap back around below zero by choosing the min and thus stop at 0
+ TimerTicks64 -= MIN (TimerTicks64, DeltaCounterVal);
+ PreviousSystemCounterVal = SystemCounterVal;
}
return MicroSeconds;
|