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Revert "ACPI: ignore FADT reset-reg-sup flag"

This reverts commit cf45013.

It breaks reboot on at least one Thinkpad T43, as reported by Jörg Otte:
 "On reboot it shuts down as normal.
  The last lines displayed are:

  >Unmounting temporary filesystems.. [OK]
  >Deactivating swap...               [OK]
  >Unmounting local filesystems...    [OK]
  >Will now restart
  >    Restarting system

  Then I hear it accessing the cd-drive, but then it's being stuck."

Jörg bisected the regression to this commit.

That commit fixes another machine (see

for details) that has a BIOS bug and doesn't support ACPI reset.
However, at least one of those other reporters no longer even has the
machine in question, and had a different workaround to begin with.
Besides, it clearly was a buggy BIOS.  Let's not break the correct case
to fix that case.

Reported-and-bisected-by: Jörg Otte <>
Cc: Len Brown <>
Cc: Peter Anvin <>
Signed-off-by: Linus Torvalds <>
  • Loading branch information...
1 parent b3dc627 commit 19244ad06b70ed84931df868583547ce1cd3a186 @torvalds torvalds committed
Showing with 4 additions and 2 deletions.
  1. +2 −1  drivers/acpi/acpica/hwxface.c
  2. +2 −1  drivers/acpi/reboot.c
3  drivers/acpi/acpica/hwxface.c
@@ -74,7 +74,8 @@ acpi_status acpi_reset(void)
/* Check if the reset register is supported */
- if (!reset_reg->address) {
+ if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER) ||
+ !reset_reg->address) {
3  drivers/acpi/reboot.c
@@ -23,7 +23,8 @@ void acpi_reboot(void)
/* Is the reset register supported? The spec says we should be
* checking the bit width and bit offset, but Windows ignores
* these fields */
- /* Ignore also acpi_gbl_FADT.flags.ACPI_FADT_RESET_REGISTER */
+ if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
+ return;
reset_value = acpi_gbl_FADT.reset_value;

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