From 75c7b6f3f6bab0432353caf634598dbdba0d6e74 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 11 Oct 2016 12:49:50 +0200 Subject: 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 Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/vdso64/clock_gettime.S | 11 ++++++++++- arch/s390/kernel/vdso64/gettimeofday.S | 11 ++++++++++- 2 files changed, 20 insertions(+), 2 deletions(-) (limited to 'arch/s390/kernel/vdso64') 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 */ -- cgit v1.2.3