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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-10-27 13:41:39 +0300
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-07-26 09:25:14 +0300
commit6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b (patch)
tree51e148a3b1e6991260af2ac51e6b1a6d5eb0f83a /arch/s390/kernel/irq.c
parent45be0a02f8110a13502fac6167a893c7c0eff432 (diff)
downloadlinux-6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b.tar.xz
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/kernel/irq.c')
-rw-r--r--arch/s390/kernel/irq.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index 6dca93b29bed..a2fdff0e730b 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -105,7 +105,8 @@ void do_IRQ(struct pt_regs *regs, int irq)
old_regs = set_irq_regs(regs);
irq_enter();
- if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
+ if (tod_after_eq(S390_lowcore.int_clock,
+ S390_lowcore.clock_comparator))
/* Serve timer interrupts first. */
clock_comparator_work();
generic_handle_irq(irq);