1 files changed, 51 insertions, 0 deletions
diff --git a/ArmPkg/Library/ArmGicArchLib/Arm/ArmGicArchLib.c b/ArmPkg/Library/ArmGicArchLib/Arm/ArmGicArchLib.c
new file mode 100644
index 0000000000..f256de7046
--- /dev/null
+++ b/ArmPkg/Library/ArmGicArchLib/Arm/ArmGicArchLib.c
@@ -0,0 +1,51 @@
+/** @file
+*
+*  Copyright (c) 2014, ARM Limited. All rights reserved.
+*
+*  This program and the accompanying materials are licensed and made available
+*  under the terms and conditions of the BSD License which accompanies this
+*  distribution.  The full text of the license may be found at
+*  http://opensource.org/licenses/bsd-license.php
+*
+*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+*
+**/
+
+#include <Library/ArmLib.h>
+#include <Library/ArmGicLib.h>
+
+ARM_GIC_ARCH_REVISION
+EFIAPI
+ArmGicGetSupportedArchRevision (
+  VOID
+  )
+{
+  UINT32    IccSre;
+
+  // Ideally we would like to use the GICC IIDR Architecture version here, but
+  // this does not seem to be very reliable as the implementation could easily
+  // get it wrong. It is more reliable to check if the GICv3 System Register
+  // feature is implemented on the CPU. This is also convenient as our GICv3
+  // driver requires SRE. If only Memory mapped access is available we try to
+  // drive the GIC as a v2.
+  if (ArmReadIdPfr1 () & ARM_PFR1_GIC) {
+    // Make sure System Register access is enabled (SRE). This depends on the
+    // higher privilege level giving us permission, otherwise we will either
+    // cause an exception here, or the write doesn't stick in which case we need
+    // to fall back to the GICv2 MMIO interface.
+    // Note: We do not need to set ICC_SRE_EL2.Enable because the OS is started
+    // at the same exception level.
+    // It is the OS responsibility to set this bit.
+    IccSre = ArmGicV3GetControlSystemRegisterEnable ();
+    if (!(IccSre & ICC_SRE_EL2_SRE)) {
+      ArmGicV3SetControlSystemRegisterEnable (IccSre| ICC_SRE_EL2_SRE);
+      IccSre = ArmGicV3GetControlSystemRegisterEnable ();
+    }
+    if (IccSre & ICC_SRE_EL2_SRE) {
+      return ARM_GIC_ARCH_REVISION_3;
+    }
+  }
+
+  return ARM_GIC_ARCH_REVISION_2;
+}