xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

s390/time: steer clocksource on STP sync events

Browse Source 
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>
This commit is contained in:
Martin Schwidefsky
2016-10-11 12:49:50 +02:00
parent 2ace06ec0d
commit 75c7b6f3f6
7 changed files with 106 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
arch/s390/kernel/vdso32/clock_gettime.S
View File

@@ -99,8 +99,27 @@ __kernel_clock_gettime:
tml %r4,0x0001 /* pending update ? loop */
jnz 11b
stcke 0(%r15) /* Store TOD clock */
lm %r0,%r1,1(%r15)
s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
lm %r0,%r1,__VDSO_TS_END(%r5) /* TOD steering end time */
s %r0,1(%r15) /* no - ts_steering_end */
sl %r1,5(%r15)
brc 3,22f
ahi %r0,-1
22: ltr %r0,%r0 /* past end of steering? */
jm 24f
srdl %r0,15 /* 1 per 2^16 */
tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */
jz 23f
lcr %r0,%r0 /* negative TOD offset */
lcr %r1,%r1
je 23f
ahi %r0,-1
23: a %r0,1(%r15) /* add TOD timestamp */
al %r1,5(%r15)
brc 12,25f
ahi %r0,1
j 25f
24: lm %r0,%r1,1(%r15) /* load TOD timestamp */
25: s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
sl %r1,__VDSO_XTIME_STAMP+4(%r5)
brc 3,12f
ahi %r0,-1

23
arch/s390/kernel/vdso32/gettimeofday.S
View File

@@ -31,8 +31,27 @@ __kernel_gettimeofday:
tml %r4,0x0001 /* pending update ? loop */
jnz 1b
stcke 0(%r15) /* Store TOD clock */
lm %r0,%r1,1(%r15)
s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
lm %r0,%r1,__VDSO_TS_END(%r5) /* TOD steering end time */
s %r0,1(%r15)
sl %r1,5(%r15)
brc 3,14f
ahi %r0,-1
14: ltr %r0,%r0 /* past end of steering? */
jm 16f
srdl %r0,15 /* 1 per 2^16 */
tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */
jz 15f
lcr %r0,%r0 /* negative TOD offset */
lcr %r1,%r1
je 15f
ahi %r0,-1
15: a %r0,1(%r15) /* add TOD timestamp */
al %r1,5(%r15)
brc 12,17f
ahi %r0,1
j 17f
16: lm %r0,%r1,1(%r15) /* load TOD timestamp */
17: s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
sl %r1,__VDSO_XTIME_STAMP+4(%r5)
brc 3,3f
ahi %r0,-1