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git.proxmox.com Git - mirror_edk2.git/blob - ArmPkg/Library/ArmGicArchSecLib/ArmGicArchLib.c
3c791a245c44122066972f1d1c7339e6d65d6e12
3 * Copyright (c) 2014, ARM Limited. All rights reserved.
5 * SPDX-License-Identifier: BSD-2-Clause-Patent
9 #include <Library/ArmLib.h>
10 #include <Library/ArmGicLib.h>
14 ArmGicGetSupportedArchRevision (
20 // Ideally we would like to use the GICC IIDR Architecture version here, but
21 // this does not seem to be very reliable as the implementation could easily
22 // get it wrong. It is more reliable to check if the GICv3 System Register
23 // feature is implemented on the CPU. This is also convenient as our GICv3
24 // driver requires SRE. If only Memory mapped access is available we try to
25 // drive the GIC as a v2.
26 if (ArmHasGicSystemRegisters ()) {
27 // Make sure System Register access is enabled (SRE). This depends on the
28 // higher privilege level giving us permission, otherwise we will either
29 // cause an exception here, or the write doesn't stick in which case we need
30 // to fall back to the GICv2 MMIO interface.
31 // Note: We do not need to set ICC_SRE_EL2.Enable because the OS is started
32 // at the same exception level.
33 // It is the OS responsibility to set this bit.
34 IccSre
= ArmGicV3GetControlSystemRegisterEnable ();
35 if (!(IccSre
& ICC_SRE_EL2_SRE
)) {
36 ArmGicV3SetControlSystemRegisterEnable (IccSre
| ICC_SRE_EL2_SRE
);
37 IccSre
= ArmGicV3GetControlSystemRegisterEnable ();
40 if (IccSre
& ICC_SRE_EL2_SRE
) {
41 return ARM_GIC_ARCH_REVISION_3
;
45 return ARM_GIC_ARCH_REVISION_2
;