diff options
authorArd Biesheuvel <ard.biesheuvel@linaro.org>2016-04-12 16:09:11 +0200
committerGraeme Gregory <graeme.gregory@linaro.org>2016-04-26 11:06:53 +0100
commit80e29739690f04b5ee1a5282615fcefd7de4a374 (patch)
parent4b328319b8cd19910107ebba195d63c80f6b14c7 (diff)
arm64: acpi: add acpi=on cmdline option to prefer ACPI boot over DTtopic-disto-fixes-erp-20160426.0
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. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
2 files changed, 10 insertions, 4 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 742f69d18fc8..28a225c31fb4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index d1ce8e2f98b9..60d728620a1b 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -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;
@@ -185,10 +188,11 @@ void __init acpi_boot_table_init(void)
* Enable ACPI instead of device tree unless
* - ACPI has been disabled explicitly (acpi=off), or
* - the device tree is not empty (it has more than just a /chosen node)
- * 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)))