ARM64 / ACPI: Introduce early_param "acpi=" to enable/disable ACPI
This implements the following policy to decide whether ACPI should
be used to boot the system:
- acpi=off: ACPI will not be used to boot the system, even if there is
no alternative available (e.g., device tree is empty)
- acpi=force: only ACPI will be used to boot the system; if that fails,
there will be no fallback to alternative methods (such as device tree)
- otherwise, ACPI will be used as a fallback if the device tree turns out
to lack a platform description; the heuristic to decide this is whether
/chosen is the only node present at depth 1
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Rafael J. Wysocki <rjw@rjwysocki.net>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
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 bfcb1a6..d6c35a7 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -165,7 +165,7 @@
bytes respectively. Such letter suffixes can also be entirely omitted.
- acpi= [HW,ACPI,X86]
+ acpi= [HW,ACPI,X86,ARM64]
Advanced Configuration and Power Interface
Format: { force | off | strict | noirq | rsdt }
force -- enable ACPI if default was off
@@ -175,6 +175,7 @@
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
See also Documentation/power/runtime_pm.txt, pci=noacpi