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/** @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 (ArmReadIdPfr0 () & AARCH64_PFR0_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;
}
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