[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, 36 insertions, 0 deletions

diff --git a/include/asm-s390/timex.h b/include/asm-s390/timex.h
index 9ee5d8013796..5cbd55cb40ce 100644
--- a/include/asm-s390/timex.h
+++ b/include/asm-s390/timex.h
@@ -11,6 +11,41 @@
 #ifndef _ASM_S390_TIMEX_H
 #define _ASM_S390_TIMEX_H
 
+/* Inline functions for clock register access. */
+static inline int set_clock(__u64 time)
+{
+        int cc;
+
+        asm volatile(
+                "   sck   0(%2)\n"
+                "   ipm   %0\n"
+                "   srl   %0,28\n"
+                : "=d" (cc) : "m" (time), "a" (&time) : "cc");
+        return cc;
+}
+
+static inline int store_clock(__u64 *time)
+{
+        int cc;
+
+        asm volatile(
+                "   stck  0(%2)\n"
+                "   ipm   %0\n"
+                "   srl   %0,28\n"
+                : "=d" (cc), "=m" (*time) : "a" (time) : "cc");
+        return cc;
+}
+
+static inline void set_clock_comparator(__u64 time)
+{
+        asm volatile("sckc 0(%1)" : : "m" (time), "a" (&time));
+}
+
+static inline void store_clock_comparator(__u64 *time)
+{
+        asm volatile("stckc 0(%1)" : "=m" (*time) : "a" (time));
+}
+
 #define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
 
 typedef unsigned long long cycles_t;
@@ -32,6 +67,7 @@ static inline cycles_t get_cycles(void)
         return (cycles_t) get_clock() >> 2;
 }
 
+int get_sync_clock(unsigned long long *clock);
 void init_cpu_timer(void);
 
 #endif