Architectures and Processors forum GIC-v3: optional asymetric / legacy support

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GIC-v3: optional asymetric / legacy support

Vincent Siles over 7 years ago

Hi,

how can I check if the GIC-v3 I am using has support for the optional asymetric / legacy support ?

Best,

V.

0 Ash Wilding over 7 years ago

Hi,
From §10.1.2 of the GICv3 Architecture Reference Manual (ARM IHI0069C):
Legacy operation is a deprecated feature. In an implementation that does not support legacy operation the following
bits, where implemented, are RAO/WI:
    • ICC_SRE_EL1.SRE.
    • ICC_SRE_EL2.SRE.
    • ICC_SRE_EL3.SRE.
    • ICC_SRE.SRE.
    • ICC_HSRE.SRE.
    • ICC_MSRE.SRE.
    • GICD_CTLR.ARE_NS.
    • GICD_CTLR.ARE_S.
A consequence of this is that if a GICv3 implementation supports legacy operation, it will be in legacy mode at reset; so if you're not in legacy mode at reset, your GICv3 implementation does not support legacy operation.
Hope that helps,
Ash.
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0 Vincent Siles over 7 years ago in reply to Ash Wilding

Ok, so I will need to patch u-boot to check very early, since I'm not the first one to mess with ICC_SRE_EL3.SRE
Thank you !
V.
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