arm64: Update booting requirements for GICv3 in GICv2 mode
The current requirements do not describe the case where a GICv3
system gets booted with system register access disabled, and
expect the kernel to drive GICv3 in GICv2 mode.
Describe the expected settings for that particular case.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
index 7d9d3c2..369a4f4 100644
--- a/Documentation/arm64/booting.txt
+++ b/Documentation/arm64/booting.txt
@@ -173,13 +173,22 @@
the kernel image will be entered must be initialised by software at a
higher exception level to prevent execution in an UNKNOWN state.
- For systems with a GICv3 interrupt controller:
+ For systems with a GICv3 interrupt controller to be used in v3 mode:
- If EL3 is present:
ICC_SRE_EL3.Enable (bit 3) must be initialiased to 0b1.
ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b1.
- If the kernel is entered at EL1:
ICC.SRE_EL2.Enable (bit 3) must be initialised to 0b1
ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b1.
+ - The DT or ACPI tables must describe a GICv3 interrupt controller.
+
+ For systems with a GICv3 interrupt controller to be used in
+ compatibility (v2) mode:
+ - If EL3 is present:
+ ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b0.
+ - If the kernel is entered at EL1:
+ ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b0.
+ - The DT or ACPI tables must describe a GICv2 interrupt controller.
The requirements described above for CPU mode, caches, MMUs, architected
timers, coherency and system registers apply to all CPUs. All CPUs must