ArmPlatformPkg/PrePiHobListPointerLib: use thread ID register

This updates the PrePiHobListPointerLib implementation in ArmPlatformPkg
to move away from ArmPlatformGlobalVariableLib and instead use the thread
ID CPU registers (TPIDRURW and TPIDR_EL0 for v7 and v8, respectively)
for storing the HobList pointer.

Since PrePiHobListPointerLib is specific to PrePi (where PEI core is skipped)
we can share these registers with the PEI services table pointer. By the
same reasoning, the PEI services table pointer and the HobList pointer
already shared the same offset in the ArmPlatformGlobalVariable array.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18982 6f19259b-4bc3-4df7-8a09-765794883524

ArmPlatformPkg/ArmPlatformPkg.dec

@@ -87,7 +87,8 @@
   # PeiServicePtr and HobListPtr shares the same location in the PEI Global Variable list
   # PeiServicePtr is only valid with PEI Core and HobListPtr only when the PEI Core is skipped.
   gArmPlatformTokenSpaceGuid.PcdPeiServicePtrGlobalOffset|0x0|UINT32|0x00000017
-  gArmPlatformTokenSpaceGuid.PcdHobListPtrGlobalOffset|0x0|UINT32|0x00000018
+  ## TO BE REMOVED
+  ## gArmPlatformTokenSpaceGuid.PcdHobListPtrGlobalOffset|0x0|UINT32|0x00000018
 
   # Size to reserve in the primary core stack for SEC Global Variables
   gArmPlatformTokenSpaceGuid.PcdSecGlobalVariableSize|0x0|UINT32|0x00000031

ArmPlatformPkg/Library/PrePiHobListPointerLib/PrePiHobListPointer.c

@@ -13,10 +13,9 @@
 **/
 
 #include <PiPei.h>
-#include <Library/ArmPlatformGlobalVariableLib.h>
+#include <Library/ArmLib.h>
 #include <Library/PrePiHobListPointerLib.h>
 #include <Library/DebugLib.h>
-#include <Library/PcdLib.h>
 
 /**
   Returns the pointer to the HOB list.
@@ -32,11 +31,7 @@ PrePeiGetHobList (
   VOID
   )
 {
-  VOID* HobList;
-
-  ArmPlatformGetGlobalVariable (PcdGet32 (PcdHobListPtrGlobalOffset), sizeof(VOID*), &HobList);
-
-  return HobList;
+  return (VOID *)ArmReadTpidrurw();
 }
 
 
@@ -53,8 +48,7 @@ PrePeiSetHobList (
   IN  VOID      *HobList
   )
 {
-  ArmPlatformSetGlobalVariable (PcdGet32 (PcdHobListPtrGlobalOffset), sizeof(VOID*), &HobList);
+  ArmWriteTpidrurw((UINTN)HobList);
 
   return EFI_SUCCESS;
 }
-

ArmPlatformPkg/Library/PrePiHobListPointerLib/PrePiHobListPointerLib.inf

@@ -25,11 +25,8 @@
 
 [Packages]
   MdePkg/MdePkg.dec
-  ArmPlatformPkg/ArmPlatformPkg.dec
+  ArmPkg/ArmPkg.dec
   EmbeddedPkg/EmbeddedPkg.dec
 
 [LibraryClasses]
-  ArmPlatformGlobalVariableLib
-
-[FixedPcd.common]
-  gArmPlatformTokenSpaceGuid.PcdHobListPtrGlobalOffset
+  ArmLib