[S390] __div64_32 for 31 bit.

The clocksource infrastructure introduced with commit
ad596171ed635c51a9eef829187af100cbf8dcf7 broke 31 bit s390.
The reason is that the do_div() primitive for 31 bit always
had a restriction: it could only divide an unsigned 64 bit
integer by an unsigned 31 bit integer. The clocksource code
now uses do_div() with a base value that has the most
significant bit set. The result is that clock->cycle_interval
has a funny value which causes the linux time to jump around
like mad.
The solution is "obvious": implement a proper __div64_32
function for 31 bit s390.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b216ca659cdf..b6b42f9f0d52 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -51,6 +51,10 @@ config 64BIT
           Select this option if you have a 64 bit IBM zSeries machine
           and want to use the 64 bit addressing mode.
 
+config 32BIT
+        bool
+        default y if !64BIT
+
 config SMP
         bool "Symmetric multi-processing support"
         ---help---