[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>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/s390/s390mach.h b/drivers/s390/s390mach.h
index 7abb42a09ae2..d3ca4281a494 100644
--- a/drivers/s390/s390mach.h
+++ b/drivers/s390/s390mach.h
@@ -102,4 +102,7 @@ static inline int stcrw(struct crw *pcrw )
         return ccode;
 }
 
+#define ED_ETR_SYNC     12      /* External damage ETR sync check */
+#define ED_ETR_SWITCH   13      /* External damage ETR switch to local */
+
 #endif /* __s390mach */