ArmPkg/Library/ArmGicArchLib/ArmGicArchLib.c

   1 /** @file
   2 *
   3 *  Copyright (c) 2014, ARM Limited. All rights reserved.
   4 *
   5 *  SPDX-License-Identifier: BSD-2-Clause-Patent
   6 *
   7 **/
   8
   9 #include <Library/ArmLib.h>
  10 #include <Library/ArmGicLib.h>
  11
  12 STATIC ARM_GIC_ARCH_REVISION        mGicArchRevision;
  13
  14 RETURN_STATUS
  15 EFIAPI
  16 ArmGicArchLibInitialize (
  17   VOID
  18   )
  19 {
  20   UINT32    IccSre;
  21
  22   // Ideally we would like to use the GICC IIDR Architecture version here, but
  23   // this does not seem to be very reliable as the implementation could easily
  24   // get it wrong. It is more reliable to check if the GICv3 System Register
  25   // feature is implemented on the CPU. This is also convenient as our GICv3
  26   // driver requires SRE. If only Memory mapped access is available we try to
  27   // drive the GIC as a v2.
  28   if (ArmHasGicSystemRegisters ()) {
  29     // Make sure System Register access is enabled (SRE). This depends on the
  30     // higher privilege level giving us permission, otherwise we will either
  31     // cause an exception here, or the write doesn't stick in which case we need
  32     // to fall back to the GICv2 MMIO interface.
  33     // Note: We do not need to set ICC_SRE_EL2.Enable because the OS is started
  34     // at the same exception level.
  35     // It is the OS responsibility to set this bit.
  36     IccSre = ArmGicV3GetControlSystemRegisterEnable ();
  37     if (!(IccSre & ICC_SRE_EL2_SRE)) {
  38       ArmGicV3SetControlSystemRegisterEnable (IccSre | ICC_SRE_EL2_SRE);
  39       IccSre = ArmGicV3GetControlSystemRegisterEnable ();
  40     }
  41     if (IccSre & ICC_SRE_EL2_SRE) {
  42       mGicArchRevision = ARM_GIC_ARCH_REVISION_3;
  43       goto Done;
  44     }
  45   }
  46
  47   mGicArchRevision = ARM_GIC_ARCH_REVISION_2;
  48
  49 Done:
  50   return RETURN_SUCCESS;
  51 }
  52
  53 ARM_GIC_ARCH_REVISION
  54 EFIAPI
  55 ArmGicGetSupportedArchRevision (
  56   VOID
  57   )
  58 {
  59   return mGicArchRevision;
  60 }