From f461ddea0af8b98e2b7940eba9c693b0ee44d64a Mon Sep 17 00:00:00 2001 From: Len Brown Date: Thu, 23 Apr 2009 18:59:43 -0400 Subject: [PATCH] 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 Signed-off-by: Len Brown --- drivers/acpi/processor_idle.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 6fe121434ffb..ea23c64bd766 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -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 */ -- 2.20.1