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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-10-11 13:49:50 +0300
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2016-10-28 11:09:02 +0300
commit75c7b6f3f6bab0432353caf634598dbdba0d6e74 (patch)
treee3f6cd5d3df07a9e9f831759f8270dc3cab481ca /arch/s390/kernel/vdso64
parent2ace06ec0d997c4332582dbbb8b5e747d22c4400 (diff)
downloadlinux-75c7b6f3f6bab0432353caf634598dbdba0d6e74.tar.xz
s390/time: steer clocksource on STP sync events
On STP sync events the TOD clock will jump in time, either forward or backward. The TOD clocksource claims to be continuous but in case of an STP sync with a negative offset it is not. Subtract the offset injected by the STP sync check from the result of the TOD clocksource to make it continuous again. Add code to drift the offset towards zero with a fixed rate, steering 1 second in ~9 hours. Suggested-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/vdso64')
-rw-r--r--arch/s390/kernel/vdso64/clock_gettime.S11
-rw-r--r--arch/s390/kernel/vdso64/gettimeofday.S11
2 files changed, 20 insertions, 2 deletions
diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S
index 61541fb93dc6..9c3b12626dba 100644
--- a/arch/s390/kernel/vdso64/clock_gettime.S
+++ b/arch/s390/kernel/vdso64/clock_gettime.S
@@ -83,8 +83,17 @@ __kernel_clock_gettime:
tmll %r4,0x0001 /* pending update ? loop */
jnz 5b
stcke 0(%r15) /* Store TOD clock */
- lgf %r2,__VDSO_TK_SHIFT(%r5) /* Timekeeper shift */
lg %r1,1(%r15)
+ lg %r0,__VDSO_TS_END(%r5) /* TOD steering end time */
+ slgr %r0,%r1 /* now - ts_steering_end */
+ ltgr %r0,%r0 /* past end of steering ? */
+ jm 17f
+ srlg %r0,%r0,15 /* 1 per 2^16 */
+ tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */
+ jz 18f
+ lcgr %r0,%r0 /* negative TOD offset */
+18: algr %r1,%r0 /* add steering offset */
+17: lgf %r2,__VDSO_TK_SHIFT(%r5) /* Timekeeper shift */
sg %r1,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
msgf %r1,__VDSO_TK_MULT(%r5) /* * tk->mult */
alg %r1,__VDSO_XTIME_NSEC(%r5) /* + tk->xtime_nsec */
diff --git a/arch/s390/kernel/vdso64/gettimeofday.S b/arch/s390/kernel/vdso64/gettimeofday.S
index 6ce46707663c..b02e62f3bc12 100644
--- a/arch/s390/kernel/vdso64/gettimeofday.S
+++ b/arch/s390/kernel/vdso64/gettimeofday.S
@@ -31,7 +31,16 @@ __kernel_gettimeofday:
jnz 0b
stcke 0(%r15) /* Store TOD clock */
lg %r1,1(%r15)
- sg %r1,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
+ lg %r0,__VDSO_TS_END(%r5) /* TOD steering end time */
+ slgr %r0,%r1 /* now - ts_steering_end */
+ ltgr %r0,%r0 /* past end of steering ? */
+ jm 6f
+ srlg %r0,%r0,15 /* 1 per 2^16 */
+ tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */
+ jz 7f
+ lcgr %r0,%r0 /* negative TOD offset */
+7: algr %r1,%r0 /* add steering offset */
+6: sg %r1,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
msgf %r1,__VDSO_TK_MULT(%r5) /* * tk->mult */
alg %r1,__VDSO_XTIME_NSEC(%r5) /* + tk->xtime_nsec */
lg %r0,__VDSO_XTIME_SEC(%r5) /* tk->xtime_sec */