arm64: acpi: add acpi=on cmdline option to prefer ACPI boot over DT
If both ACPI and DT platform descriptions are available, and the
kernel was configured at build time to support both flavours, the
default policy is to prefer DT over ACPI, and preferring ACPI over
DT while still allowing DT as a fallback is not possible.
Since some enterprise features (such as RAS) depend on ACPI, it may
be desirable for, e.g., distro installers to prefer ACPI boot but
fall back to DT rather than failing completely if no ACPI tables are
available.
So introduce the 'acpi=on' kernel command line parameter for arm64,
which signifies that ACPI should be used if available, and DT should
only be used as a fallback.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ecc74fa..748129c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -167,16 +167,18 @@
acpi= [HW,ACPI,X86,ARM64]
Advanced Configuration and Power Interface
- Format: { force | off | strict | noirq | rsdt |
+ Format: { force | on | off | strict | noirq | rsdt |
copy_dsdt }
force -- enable ACPI if default was off
+ on -- enable ACPI but allow fallback to DT [arm64]
off -- disable ACPI if default was on
noirq -- do not use ACPI for IRQ routing
strict -- Be less tolerant of platforms that are not
strictly ACPI specification compliant.
rsdt -- prefer RSDT over (default) XSDT
copy_dsdt -- copy DSDT to memory
- For ARM64, ONLY "acpi=off" or "acpi=force" are available
+ For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
+ are available
See also Documentation/power/runtime_pm.txt, pci=noacpi