Debug Enable in ppc44x_idle

I am working on a ppc440gx platform and came across ppc44x_idle()
function. the actual requirement is to enable WAIT_STATE Enable bit
(MSR_WE) and External Interrupt enable bit (MSR_EE) on MSR. But for
ppc440, i see that MSR_DE bit (Debug Interrupt Enable) is also
enabled.

Any idea why MSR_DE enabled in ppc44x_idle() function ?

Thanks
Vineeth