tree 649e14d532e17231225a042a7c9a3d9207ad91ee
parent c1821c2e9711adc3cd298a16b7237c92a2cee78d
author Martin Schwidefsky <schwidefsky@de.ibm.com> 1170706699 +0100
committer Martin Schwidefsky <schwidefsky@de.ibm.com> 1170706699 +0100

[S390] ETR support.

This patch adds support for clock synchronization to an external time
reference (ETR). The external time reference sends an oscillator
signal and a synchronization signal every 2^20 microseconds to keep
the TOD clocks of all connected servers in sync. For availability
two ETR units can be connected to a machine. If the clock deviates
for more than the sync-check tolerance all cpus get a machine check
that indicates that the clock is out of sync. For the lovely details
how to get the clock back in sync see the code below.

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