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Subject[PATCH v9 09/21] ARM64 / ACPI: Introduce early_param "acpi=" to enable/disable ACPI
Date
From: Al Stone <al.stone@linaro.org>

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>
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>
---
Documentation/kernel-parameters.txt | 3 ++-
arch/arm64/include/asm/acpi.h | 7 +++++
arch/arm64/kernel/acpi.c | 52 +++++++++++++++++++++++++++++++++----
3 files changed, 56 insertions(+), 6 deletions(-)

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 @@ 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,ARM64]
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" or "acpi=force" are available

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

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 40e0924..c5a9b97 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -39,6 +39,13 @@ static inline void disable_acpi(void)
acpi_noirq = 1;
}

+static inline void enable_acpi(void)
+{
+ acpi_disabled = 0;
+ acpi_pci_disabled = 0;
+ acpi_noirq = 0;
+}
+
/*
* It's used from ACPI core in kdump to boot UP system with SMP kernel,
* with this check the ACPI core will not override the CPU index
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index f052e7a..bdcc9fc 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -22,15 +22,49 @@
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/memblock.h>
+#include <linux/of_fdt.h>
#include <linux/smp.h>

-int acpi_noirq; /* skip ACPI IRQ initialization */
-int acpi_disabled;
+int acpi_noirq = 1; /* skip ACPI IRQ initialization */
+int acpi_disabled = 1;
EXPORT_SYMBOL(acpi_disabled);

-int acpi_pci_disabled; /* skip ACPI PCI scan and IRQ initialization */
+int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */
EXPORT_SYMBOL(acpi_pci_disabled);

+static bool __initdata param_acpi_off;
+static bool __initdata param_acpi_force;
+
+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)
+ param_acpi_off = true;
+ else if (strcmp(arg, "force") == 0) /* force ACPI to be enabled */
+ param_acpi_force = true;
+ else
+ return -EINVAL; /* Core will print when we return error */
+
+ return 0;
+}
+early_param("acpi", parse_acpi);
+
+static int __init dt_scan_depth1_nodes(unsigned long node,
+ const char *uname, int depth,
+ void *data)
+{
+ /*
+ * Return 1 as soon as we encounter a node at depth 1 that is
+ * not the /chosen node.
+ */
+ if (depth == 1 && (strcmp(uname, "chosen") != 0))
+ return 1;
+ return 0;
+}
+
/*
* __acpi_map_table() will be called before page_init(), so early_ioremap()
* or early_memremap() should be called here to for ACPI table mapping.
@@ -83,10 +117,18 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
*/
void __init acpi_boot_table_init(void)
{
- /* If acpi_disabled, bail out */
- if (acpi_disabled)
+ /*
+ * 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)
+ */
+ if (param_acpi_off ||
+ (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
return;

+ enable_acpi();
+
/* Initialize the ACPI boot-time table parser. */
if (acpi_table_init()) {
disable_acpi();
--
1.9.1


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