From: Udo A. Steinberg The chipset doc for IHC4 tells us: 1.In general, software should not attempt any non-posted accesses during arbiter disable except to the ICH4's power management registers. This implies that interrupt handlers for any unmasked hardware interrupts and SMI/NMI should check ARB_DIS status before reading from ICH devices. So it's not a good idea to access ICH devices after arbiter shut down. Signed-off-by: Udo A. Steinberg Signed-off-by: Thomas Gleixner Cc: Len Brown Signed-off-by: Andrew Morton --- drivers/acpi/processor_idle.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletion(-) diff -puN drivers/acpi/processor_idle.c~acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown drivers/acpi/processor_idle.c --- a/drivers/acpi/processor_idle.c~acpi-move-timer-broadcast-and-pmtimer-access-before-c3-arbiter-shutdown +++ a/drivers/acpi/processor_idle.c @@ -1009,6 +1009,12 @@ static int acpi_idle_enter_c3(struct cpu return 0; } + /* + * Must be done before busmaster disable as we might need to + * access HPET! + */ + acpi_state_timer_broadcast(pr, cx, 1); + /* disable bus master */ if (pr->flags.bm_check) { spin_lock(&c3_lock); @@ -1028,7 +1034,6 @@ static int acpi_idle_enter_c3(struct cpu /* Get start time (ticks) */ t1 = inl(acpi_gbl_FADT.xpm_timer_block.address); - acpi_state_timer_broadcast(pr, cx, 1); acpi_idle_do_entry(cx); t2 = inl(acpi_gbl_FADT.xpm_timer_block.address); _