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Commit b10d79f7 authored by Al Stone's avatar Al Stone Committed by Will Deacon
Browse files

ARM64 / ACPI: Introduce early_param "acpi=" to enable/disable ACPI 



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>
Acked-by: default avatarOlof Johansson <olof@lixom.net>
Acked-by: default avatarGrant Likely <grant.likely@linaro.org>
Tested-by: default avatarTimur Tabi <timur@codeaurora.org>
Signed-off-by: default avatarAl Stone <al.stone@linaro.org>
Signed-off-by: default avatarGraeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: default avatarHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent a9cb97fe

Documentation/kernel-parameters.txt

+2 −1
Original line number Diff line number Diff line
@@ -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

arch/arm64/include/asm/acpi.h

+7 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/acpi.c

+47 −5
Original line number Diff line number Diff line
@@ -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 param_acpi_off __initdata;

static bool param_acpi_force __initdata;



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();