x86: add ACPI reboot option

Add the ability to reboot an x86_64 based machine using the RESET_REG in the
FADT ACPI table.

Signed-off-by: Aaron Durbin <adurbin@google.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 14 insertions, 2 deletions

diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 945311840a10..d7a333258682 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -110,12 +110,15 @@ Idle loop
 
 Rebooting
 
-   reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
+   reboot=b[ios] | t[riple] | k[bd] | a[cpi] [, [w]arm | [c]old]
    bios   Use the CPU reboot vector for warm reset
    warm   Don't set the cold reboot flag
    cold   Set the cold reboot flag
    triple Force a triple fault (init)
    kbd    Use the keyboard controller. cold reset (default)
+   acpi   Use the ACPI RESET_REG in the FADT. If ACPI is not configured or the
+          ACPI reset does not work, the reboot path attempts the reset using
+          the keyboard controller.
 
    Using warm reset will be much faster especially on big memory
    systems because the BIOS will not go through the memory check.
diff --git a/arch/x86/kernel/reboot_64.c b/arch/x86/kernel/reboot_64.c
index 53620a92a8fd..307f996a3933 100644
--- a/arch/x86/kernel/reboot_64.c
+++ b/arch/x86/kernel/reboot_64.c
@@ -9,6 +9,7 @@
 #include <linux/pm.h>
 #include <linux/kdebug.h>
 #include <linux/sched.h>
+#include <acpi/reboot.h>
 #include <asm/io.h>
 #include <asm/delay.h>
 #include <asm/desc.h>
@@ -29,7 +30,8 @@ EXPORT_SYMBOL(pm_power_off);
 static long no_idt[3];
 static enum { 
         BOOT_TRIPLE = 't',
-        BOOT_KBD = 'k'
+        BOOT_KBD = 'k',
+        BOOT_ACPI = 'a'
 } reboot_type = BOOT_KBD;
 static int reboot_mode = 0;
 int reboot_force;
@@ -39,6 +41,7 @@ int reboot_force;
    cold   Set the cold reboot flag
    triple Force a triple fault (init)
    kbd    Use the keyboard controller. cold reset (default)
+   acpi   Use the RESET_REG in the FADT
    force  Avoid anything that could hang.
  */ 
 static int __init reboot_setup(char *str)
@@ -54,6 +57,7 @@ static int __init reboot_setup(char *str)
                         break;
 
                 case 't':
+                case 'a':
                 case 'b':
                 case 'k':
                         reboot_type = *str;
@@ -146,6 +150,11 @@ void machine_emergency_restart(void)
 
                         reboot_type = BOOT_KBD;
                         break;
+
+                case BOOT_ACPI:
+                        acpi_reboot();
+                        reboot_type = BOOT_KBD;
+                        break;
                 }      
         }      
 }