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| author |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-10-27 12:41:39 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-07-26 08:25:14 +0200 |
| commit | 6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b (patch) | |
| tree | 51e148a3b1e6991260af2ac51e6b1a6d5eb0f83a /arch/s390/kernel/head64.S | |
| parent | s390/sclp: single increment assignment control (diff) | |
| download | linux-dev-6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b.tar.xz linux-dev-6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b.zip | |
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/head64.S')
| -rw-r--r-- | arch/s390/kernel/head64.S | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S index 31c91f24e562..0d8f2a858ced 100644 --- a/arch/s390/kernel/head64.S +++ b/arch/s390/kernel/head64.S @@ -21,8 +21,8 @@ ENTRY(startup_continue) xc __LC_LPP+1(7,0),__LC_LPP+1 # clear lpp and current_pid mvi __LC_LPP,0x80 # and set LPP_MAGIC .insn s,0xb2800000,__LC_LPP # load program parameter -0: larl %r1,sched_clock_base_cc - mvc 0(8,%r1),__LC_LAST_UPDATE_CLOCK +0: larl %r1,tod_clock_base + mvc 0(16,%r1),__LC_BOOT_CLOCK larl %r13,.LPG1 # get base lctlg %c0,%c15,.Lctl-.LPG1(%r13) # load control registers lg %r12,.Lparmaddr-.LPG1(%r13) # pointer to parameter area |