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Subject[PATCH] arm64/acpi: make ACPI boot preference configurable
Date
This patch allows a user to configure ACPI to be preferred over
device-tree.

Currently for ACPI to be used a user either has to set acpi=on on the
kernel command line or make sure any device tree passed to the kernel
is empty. If the dtb passed to the kernel is non-empty then device-tree
will be chosen as the boot method of choice even if it is not correct.
To prevent this situation where a system is only intended to be booted
via ACPI a user can set this kernel configuration so it ignores
device-tree settings unless ACPI table checks fail.

Signed-off-by: Jonathan Toppins <jtoppins@redhat.com>
---

arch/arm64/Kconfig | 13 +++++++++++++
arch/arm64/kernel/acpi.c | 2 +-
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7381eeb7ef8e..da8d9ab62825 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1170,6 +1170,19 @@ config ARM64_ACPI_PARKING_PROTOCOL
protocol even if the corresponding data is present in the ACPI
MADT table.

+config ARM64_PREFER_ACPI
+ bool "Prefer usage of ACPI boot tables over device-tree"
+ depends on ACPI
+ help
+ Normally device-tree is preferred over ACPI on arm64 unless
+ explicitly preferred via kernel command line, something like: acpi=on
+ This configuration changes this default behaviour by pretending
+ the user set acpi=on on the command line. This configuration still
+ allows the user to turn acpi table parsing off via acpi=off. If
+ for some reason the table checks fail the system will still fall
+ back to using device-tree unless the user explicitly sets acpi=force
+ on the command line.
+
config CMDLINE
string "Default kernel command string"
default ""
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 7b09487ff8fb..315b001c45f1 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -44,7 +44,7 @@ int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */
EXPORT_SYMBOL(acpi_pci_disabled);

static bool param_acpi_off __initdata;
-static bool param_acpi_on __initdata;
+static bool param_acpi_on __initdata = IS_ENABLED(CONFIG_ARM64_PREFER_ACPI);
static bool param_acpi_force __initdata;

static int __init parse_acpi(char *arg)
--
2.13.6
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