Commit 6a1f5471 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon

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

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: default avatarCatalin Marinas <>
Signed-off-by: default avatarArd Biesheuvel <>
Signed-off-by: default avatarWill Deacon <>
parent 08cdac61
......@@ -167,16 +167,18 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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
......@@ -42,6 +42,7 @@ int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */
static bool param_acpi_off __initdata;
static bool param_acpi_on __initdata;
static bool param_acpi_force __initdata;
static int __init parse_acpi(char *arg)
......@@ -52,6 +53,8 @@ static int __init parse_acpi(char *arg)
/* "acpi=off" disables both ACPI table parsing and interpreter */
if (strcmp(arg, "off") == 0)
param_acpi_off = true;
else if (strcmp(arg, "on") == 0) /* prefer ACPI over DT */
param_acpi_on = true;
else if (strcmp(arg, "force") == 0) /* force ACPI to be enabled */
param_acpi_force = true;
......@@ -198,10 +201,11 @@ void __init acpi_boot_table_init(void)
* - ACPI has been disabled explicitly (acpi=off), or
* - the device tree is not empty (it has more than just a /chosen node,
* and a /hypervisor node when running on Xen)
* and ACPI has not been force enabled (acpi=force)
* and ACPI has not been [force] enabled (acpi=on|force)
if (param_acpi_off ||
(!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
(!param_acpi_on && !param_acpi_force &&
of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
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