If the clkdm is in HW_AUTO, I can get DSS in sleep(STBYST and IDLEST all
set). Is this helpful? Can we just leave modulemode on all the time?
That'll be the best :)

Is everything around DSS enabled by default in omap2plus? If so, I
haven't seen Tero (who has been working on getting OMAP4 to sleep)
complain about DSS causing him any trouble. So you should be good
with whats already there atleast from 'not-gating-sleep' point of
view.