From: Al Stone <redacted>

Introduce one early parameters "off" for "acpi" to disable ACPI on
ARM64.

This ensures the kernel uses the DT on a platform that provides both
ACPI tables and DT.

Signed-off-by: Al Stone <redacted>
Signed-off-by: Graeme Gregory <redacted>
Signed-off-by: Hanjun Guo <redacted>
---
 Documentation/kernel-parameters.txt |    3 ++-
 arch/arm64/kernel/acpi.c            |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5ae8608..9dfb1d8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt

@@ -165,7 +165,7 @@ multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 bytes respectively. Such letter suffixes can also be entirely omitted.
 
 
-	acpi=		[HW,ACPI,X86]
+	acpi=		[HW,ACPI,X86,ARM]

 			Advanced Configuration and Power Interface
 			Format: { force | off | strict | noirq | rsdt }
 			force -- enable ACPI if default was off

@@ -175,6 +175,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				strictly ACPI specification compliant.
 			rsdt -- prefer RSDT over (default) XSDT
 			copy_dsdt -- copy DSDT to memory
+			For ARM64, ONLY "acpi=off" is available.

 			See also Documentation/power/runtime_pm.txt, pci=noacpi
 

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 9252f72..693da7f 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c

@@ -67,3 +67,18 @@ void __init acpi_boot_table_init(void)
 	if (acpi_table_init())
 		disable_acpi();
 }
+
+static int __init parse_acpi(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+
+	/* "acpi=off" disables both ACPI table parsing and interpreter */
+	if (strcmp(arg, "off") == 0)
+		disable_acpi();
+	else
+		return -EINVAL;	/* Core will print when we return error */