[PATCH 1/3] s390/time: STP sync clock correction

[Tim Gardner]

From: Martin Schwidefsky <schwidefsky at de.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1644505

The sync clock operation of the channel subsystem call for STP delivers
the TOD clock difference as a result. Use this TOD clock difference
instead of the difference between the TOD timestamps before and after
the sync clock operation.

Signed-off-by: Martin Schwidefsky <schwidefsky at de.ibm.com>
(cherry picked from commit 2f82f57763d97700788cf228de1cf30ffd4153b4)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 arch/s390/include/asm/cio.h |  2 +-
 arch/s390/kernel/time.c     | 11 +++++------
 drivers/s390/cio/chsc.c     |  8 ++++++--
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/s390/include/asm/cio.h b/arch/s390/include/asm/cio.h
index d1e7b0a..f7ed88c 100644
--- a/arch/s390/include/asm/cio.h
+++ b/arch/s390/include/asm/cio.h
@@ -320,7 +320,7 @@ struct cio_iplinfo {
 extern int cio_get_iplinfo(struct cio_iplinfo *iplinfo);
 
 /* Function from drivers/s390/cio/chsc.c */
-int chsc_sstpc(void *page, unsigned int op, u16 ctrl);
+int chsc_sstpc(void *page, unsigned int op, u16 ctrl, u64 *clock_delta);
 int chsc_sstpi(void *page, void *result, size_t size);
 
 #endif
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 99f84ac31..1a94242 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -1460,7 +1460,7 @@ static void __init stp_reset(void)
 	int rc;
 
 	stp_page = (void *) get_zeroed_page(GFP_ATOMIC);
-	rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000);
+	rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000, NULL);
 	if (rc == 0)
 		set_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags);
 	else if (stp_online) {
@@ -1560,11 +1560,10 @@ static int stp_sync_clock(void *data)
 	    stp_info.todoff[2] || stp_info.todoff[3] ||
 	    stp_info.tmd != 2) {
 		old_clock = get_tod_clock();
-		rc = chsc_sstpc(stp_page, STP_OP_SYNC, 0);
+		rc = chsc_sstpc(stp_page, STP_OP_SYNC, 0, &clock_delta);
 		if (rc == 0) {
-			new_clock = get_tod_clock();
+			new_clock = old_clock + clock_delta;
 			delta = adjust_time(old_clock, new_clock, 0);
-			clock_delta = new_clock - old_clock;
 			atomic_notifier_call_chain(&s390_epoch_delta_notifier,
 						   0, &clock_delta);
 			fixup_clock_comparator(delta);
@@ -1596,12 +1595,12 @@ static void stp_work_fn(struct work_struct *work)
 	mutex_lock(&stp_work_mutex);
 
 	if (!stp_online) {
-		chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000);
+		chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000, NULL);
 		del_timer_sync(&stp_timer);
 		goto out_unlock;
 	}
 
-	rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0xb0e0);
+	rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0xb0e0, NULL);
 	if (rc)
 		goto out_unlock;
 
diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c
index 1e16331..c382593 100644
--- a/drivers/s390/cio/chsc.c
+++ b/drivers/s390/cio/chsc.c
@@ -1180,7 +1180,7 @@ exit:
 EXPORT_SYMBOL_GPL(css_general_characteristics);
 EXPORT_SYMBOL_GPL(css_chsc_characteristics);
 
-int chsc_sstpc(void *page, unsigned int op, u16 ctrl)
+int chsc_sstpc(void *page, unsigned int op, u16 ctrl, u64 *clock_delta)
 {
 	struct {
 		struct chsc_header request;
@@ -1190,7 +1190,9 @@ int chsc_sstpc(void *page, unsigned int op, u16 ctrl)
 		unsigned int ctrl : 16;
 		unsigned int rsvd2[5];
 		struct chsc_header response;
-		unsigned int rsvd3[7];
+		unsigned int rsvd3[3];
+		u64 clock_delta;
+		unsigned int rsvd4[2];
 	} __attribute__ ((packed)) *rr;
 	int rc;
 
@@ -1204,6 +1206,8 @@ int chsc_sstpc(void *page, unsigned int op, u16 ctrl)
 	if (rc)
 		return -EIO;
 	rc = (rr->response.code == 0x0001) ? 0 : -EIO;
+	if (clock_delta)
+		*clock_delta = rr->clock_delta;
 	return rc;
 }
 
-- 
2.7.4