[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, 15 insertions, 2 deletions

diff --git a/drivers/s390/s390mach.c b/drivers/s390/s390mach.c
index 442d63470428..806bb1a921eb 100644
--- a/drivers/s390/s390mach.c
+++ b/drivers/s390/s390mach.c
@@ -15,7 +15,7 @@
 #include <linux/time.h>
 #include <linux/device.h>
 #include <linux/kthread.h>
-
+#include <asm/etr.h>
 #include <asm/lowcore.h>
 #include <asm/cio.h>
 #include "cio/cio.h"
@@ -466,6 +466,19 @@ s390_do_machine_check(struct pt_regs *regs)
                         s390_handle_damage("unable to revalidate registers.");
         }
 
+        if (mci->cd) {
+                /* Timing facility damage */
+                s390_handle_damage("TOD clock damaged");
+        }
+
+        if (mci->ed && mci->ec) {
+                /* External damage */
+                if (S390_lowcore.external_damage_code & (1U << ED_ETR_SYNC))
+                        etr_sync_check();
+                if (S390_lowcore.external_damage_code & (1U << ED_ETR_SWITCH))
+                        etr_switch_to_local();
+        }
+
         if (mci->se)
                 /* Storage error uncorrected */
                 s390_handle_damage("received storage error uncorrected "
@@ -504,7 +517,7 @@ static int
 machine_check_init(void)
 {
         init_MUTEX_LOCKED(&m_sem);
-        ctl_clear_bit(14, 25);  /* disable external damage MCH */
+        ctl_set_bit(14, 25);    /* enable external damage MCH */
         ctl_set_bit(14, 27);    /* enable system recovery MCH */
 #ifdef CONFIG_MACHCHK_WARNING
         ctl_set_bit(14, 24);    /* enable warning MCH */