[S390] ETR support.
This patch adds support for clock synchronization to an external time
reference (ETR). The external time reference sends an oscillator
signal and a synchronization signal every 2^20 microseconds to keep
the TOD clocks of all connected servers in sync. For availability
two ETR units can be connected to a machine. If the clock deviates
for more than the sync-check tolerance all cpus get a machine check
that indicates that the clock is out of sync. For the lovely details
how to get the clock back in sync see the code below.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index cb155d9..08f9a4d 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -457,9 +457,10 @@
/* Setup the cpu */
cpu_init();
preempt_disable();
- /* init per CPU timer */
+ /* Enable TOD clock interrupts on the secondary cpu. */
init_cpu_timer();
#ifdef CONFIG_VIRT_TIMER
+ /* Enable cpu timer interrupts on the secondary cpu. */
init_cpu_vtimer();
#endif
/* Enable pfault pseudo page faults on this cpu. */