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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-10-27 12:41:39 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-07-26 08:25:14 +0200
commit6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b (patch)
tree51e148a3b1e6991260af2ac51e6b1a6d5eb0f83a /arch/s390/lib
parent45be0a02f8110a13502fac6167a893c7c0eff432 (diff)
downloadlinux-6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b.tar.bz2
s390/time: add support for the TOD clock epoch extension
The TOD epoch extension adds 8 epoch bits to the TOD clock to provide a continuous clock after 2042/09/17. The store-clock-extended (STCKE) instruction will store the epoch index in the first byte of the 16 bytes stored by the instruction. The read_boot_clock64 and the read_presistent_clock64 functions need to take the additional bits into account to give the correct result after 2042/09/17. The clock-comparator register will stay 64 bit wide. The comparison of the clock-comparator with the TOD clock is limited to bytes 1 to 8 of the extended TOD format. To deal with the overflow problem due to an epoch change the clock-comparator sign control in CR0 can be used to switch the comparison of the 64-bit TOD clock with the clock-comparator to a signed comparison. The decision between the signed vs. unsigned clock-comparator comparisons is done at boot time. Only if the TOD clock is in the second half of a 142 year epoch the signed comparison is used. This solves the epoch overflow issue as long as the machine is booted at least once in an epoch. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/lib')
-rw-r--r--arch/s390/lib/delay.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
index 92e90e40b6fb..7f17555ad4d5 100644
--- a/arch/s390/lib/delay.c
+++ b/arch/s390/lib/delay.c
@@ -57,7 +57,7 @@ static void __udelay_enabled(unsigned long long usecs)
end = get_tod_clock_fast() + (usecs << 12);
do {
clock_saved = 0;
- if (end < S390_lowcore.clock_comparator) {
+ if (tod_after(S390_lowcore.clock_comparator, end)) {
clock_saved = local_tick_disable();
set_clock_comparator(end);
}