On R4k DECstations the Halt button is wired to the NMI processor input
rather than an ordinary interrupt input such as on R3k DECstations.  This
is possible with a different design of the CPU daughtercard that routes
the Halt button line from the baseboard connector.  Additionally the
interrupt input has been reused for a different purpose on the KN04 and
KN05 R4k CPU daughtercards so it is better kept masked.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6705/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>