From 16b7aff06b4379eaac48dc6e78c7a3944c0bdbad Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Mon, 2 Feb 2015 12:01:48 +0000
Subject: ArmPkg: ArmArchTimerLib: conditionally rebase to actual timer
 frequency

Allow a platform to set PcdArmArchTimerFreqInHz to zero, and consider it a
request to use the actual timer frequency.

No global variable is introduced, so that the library can be used in PEIMs
that execute from flash.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Olivier Martin <Olivier.martin@arm.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16691 6f19259b-4bc3-4df7-8a09-765794883524
---
 ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c | 58 ++++++++++++++++--------
 1 file changed, 38 insertions(+), 20 deletions(-)

diff --git a/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c b/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c
index 51d7ce9..a0e4f58 100644
--- a/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c
+++ b/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c
@@ -37,28 +37,29 @@ TimerConstructor (
     UINTN TimerFreq;
 
     //
-    // Check if Architectural Timer frequency is valid (should not be 0).
+    // Check if Architectural Timer frequency is pre-determined by the platform
+    // (ie. nonzero).
     //
-    ASSERT (PcdGet32 (PcdArmArchTimerFreqInHz));
-
-    //
-    // Check if ticks/uS is not 0. The Architectural timer runs at constant
-    // frequency, irrespective of CPU frequency. According to General Timer
-    // Ref manual, lower bound of the frequency is in the range of 1-10MHz.
-    //
-    ASSERT (TICKS_PER_MICRO_SEC);
+    if (PcdGet32 (PcdArmArchTimerFreqInHz) != 0) {
+      //
+      // Check if ticks/uS is not 0. The Architectural timer runs at constant
+      // frequency, irrespective of CPU frequency. According to General Timer
+      // Ref manual, lower bound of the frequency is in the range of 1-10MHz.
+      //
+      ASSERT (TICKS_PER_MICRO_SEC);
 
 #ifdef MDE_CPU_ARM
-    //
-    // Only set the frequency for ARMv7. We expect the secure firmware to
-    // have already done it.
-    // If the security extension is not implemented, set Timer Frequency
-    // here.
-    //
-    if ((ArmReadIdPfr1 () & ARM_PFR1_SEC) == 0x0) {
-      ArmGenericTimerSetTimerFreq (PcdGet32 (PcdArmArchTimerFreqInHz));
-    }
+      //
+      // Only set the frequency for ARMv7. We expect the secure firmware to
+      // have already done it.
+      // If the security extension is not implemented, set Timer Frequency
+      // here.
+      //
+      if ((ArmReadIdPfr1 () & ARM_PFR1_SEC) == 0x0) {
+        ArmGenericTimerSetTimerFreq (PcdGet32 (PcdArmArchTimerFreqInHz));
+      }
 #endif
+    }
 
     //
     // Architectural Timer Frequency must be set in the Secure privileged
@@ -92,14 +93,31 @@ MicroSecondDelay (
 {
   UINT64 TimerTicks64;
   UINT64 SystemCounterVal;
+  UINT64 (EFIAPI
+          *MultU64xN) (
+            IN UINT64 Multiplicand,
+            IN UINTN  Multiplier
+            );
+  UINTN TimerFreq;
+
+#ifdef MDE_CPU_ARM
+  MultU64xN = MultU64x32;
+#else
+  MultU64xN = MultU64x64;
+#endif
+
+  TimerFreq = PcdGet32 (PcdArmArchTimerFreqInHz);
+  if (TimerFreq == 0) {
+    TimerFreq = ArmGenericTimerGetTimerFreq ();
+  }
 
   // Calculate counter ticks that can represent requested delay:
   //  = MicroSeconds x TICKS_PER_MICRO_SEC
   //  = MicroSeconds x Frequency.10^-6
   TimerTicks64 = DivU64x32 (
-                   MultU64x32 (
+                   MultU64xN (
                      MicroSeconds,
-                     PcdGet32 (PcdArmArchTimerFreqInHz)
+                     TimerFreq
                      ),
                    1000000U
                    );
-- 
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