On Tue, Aug 30, 2016 at 09:21:16PM -0700, Douglas Anderson wrote:

In this patch we actually block returning from the set_voltage() call
until we've finished delaying.  A future patch atop this one might
choose to return more immediately and let the voltages fall in the
background.  That would possibly to allow us to cancel a slow downward
decay if there was a request to go back up.

We already have mechanisms in the core for drivers to tell the core how
long a ramp they need for a given voltage transition - you should extend
them (probably needs a set_voltage_time() operation adding) so that
anything like this can be done in the core rather than open coded in
drivers.