x86, clockevents: add C1E aware idle function

C1E on AMD machines is like C3 but without control from the OS. Up to
now we disabled the local apic timer for those machines as it stops
when the CPU goes into C1E. This excludes those machines from high
resolution timers / dynamic ticks, which hurts especially X2 based
laptops.

The current boot time C1E detection has another, more serious flaw
as well: some BIOSes do not enable C1E until the ACPI processor module
is loaded. This causes systems to stop working after that point.

To work nicely with C1E enabled machines we use a separate idle
function, which checks on idle entry whether C1E was enabled in the
Interrupt Pending Message MSR. This allows us to do timer broadcasting
for C1E and covers the late enablement of C1E as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 57a1f02e5ec0..67f80c261709 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -30,6 +30,7 @@
 struct tick_device tick_broadcast_device;
 static cpumask_t tick_broadcast_mask;
 static DEFINE_SPINLOCK(tick_broadcast_lock);
+static int tick_broadcast_force;
 
 #ifdef CONFIG_TICK_ONESHOT
 static void tick_broadcast_clear_oneshot(int cpu);
@@ -232,10 +233,11 @@ static void tick_do_broadcast_on_off(void *why)
                                                      CLOCK_EVT_MODE_SHUTDOWN);
                 }
                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
-                        dev->features |= CLOCK_EVT_FEAT_DUMMY;
+                        tick_broadcast_force = 1;
                 break;
         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
-                if (cpu_isset(cpu, tick_broadcast_mask)) {
+                if (!tick_broadcast_force &&
+                    cpu_isset(cpu, tick_broadcast_mask)) {
                         cpu_clear(cpu, tick_broadcast_mask);
                         if (td->mode == TICKDEV_MODE_PERIODIC)
                                 tick_setup_periodic(dev, 0);