ACPI/hpet: prevent boot hang when hpet=force used on ICH-4M
Linux tells ICH4 users that they can (manually) invoke
"hpet=force" to enable the undocumented ICH-4M HPET.
The HPET becomes available for both clocksource and clockevents.
But as of ff69f2bba67bd45514923aaedbf40fe351787c59
(acpi: fix of pmtimer overflow that make Cx states time incorrect)
the HPET may be used via clocksource for idle accounting, and
hpet=force on an ICH4 box hangs boot.
It turns out that touching the MMIO HPET withing
the ARB_DIS part of C3 will hang the hardware.
The fix is to simply move the timer access outside
the ARB_DIS region. This is a no-op on modern hardware
because ARB_DIS is no longer used.
http://bugzilla.kernel.org/show_bug.cgi?id=13087
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 6fe1214..ea23c64 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -955,6 +955,7 @@
*/
acpi_state_timer_broadcast(pr, cx, 1);
+ kt1 = ktime_get_real();
/*
* disable bus master
* bm_check implies we need ARB_DIS
@@ -976,10 +977,7 @@
ACPI_FLUSH_CPU_CACHE();
}
- kt1 = ktime_get_real();
acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- idle_time = ktime_to_us(ktime_sub(kt2, kt1));
/* Re-enable bus master arbitration */
if (pr->flags.bm_check && pr->flags.bm_control) {
@@ -988,6 +986,8 @@
c3_cpu_count--;
spin_unlock(&c3_lock);
}
+ kt2 = ktime_get_real();
+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
/* TSC could halt in idle, so notify users */
