quoted

So why does OMAP4 have working coupled idle without the SGI check then?

Because whenever the OMAP4 CPUs enter into any power states apart from
ON, clock-domain force wakeup method us being used to wakeup
secondary CPUs. And secondly CPU RET is not supported on purpose because
of some known IP block issues.

Aha. That explains indeed why you don't need the check.

Cheers,

Peter.