Commit f461ddea authored Apr 23, 2009 by Len Brown

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 ff69f2bb
(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>

parent 09106974

drivers/acpi/processor_idle.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -955,6 +955,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
		*/
		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 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
		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 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
		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 */