Commit 9a488888 authored Oct 13, 2020 by Zhang Rui Committed by Rafael J. Wysocki Oct 16, 2020

ACPI: reboot: Avoid racing after writing to ACPI RESET_REG



According to the ACPI spec, "The system must reset immediately following
the write to the ACPI RESET_REG register.", but there are cases that the
system does not follow this and results in racing with the subsequetial
reboot mechanism, which brings unexpected behavior.

Fix this by adding a 15ms delay after writing to the ACPI RESET_REG.

Reported-by: Ghorai, Sukumar <sukumar.ghorai@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
[ rjw: Edit comment in the code and subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent cf1d2b44

drivers/acpi/reboot.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -3,6 +3,7 @@
		#include <linux/pci.h>
		#include <linux/acpi.h>
		#include <acpi/reboot.h>
		#include <linux/delay.h>

		#ifdef CONFIG_PCI
		static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
		@@ -66,4 +67,14 @@ void acpi_reboot(void)
		acpi_reset();
		break;
		}

		/*
		* Some platforms do not shut down immediately after writing to the
		* ACPI reset register, and this results in racing with the
		* subsequent reboot mechanism.
		*
		* The 15ms delay has been found to be long enough for the system
		* to reboot on the affected platforms.
		*/
		mdelay(15);
		}

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