On Mon, Jan 20, 2014 at 2:48 PM, Russell King - ARM Linux
[off-list ref] wrote:

So far so good.  Now, what about this external oscillator which has its
own separate power control.  My immediate thought is that this can be
specified via card_ext_clock - I would simply need to declare a fixed-rate
clock with either a regulator (power switch) controlled via a gpio (which
would probably be closer to the hardware) or a gpio as an enable... ah,
that requires me to write a common clock driver for that bit since this
is currently not modelled by CCF...

Jiry Sarha posted a gpio controlled clock proposal:
http://www.spinics.net/lists/devicetree/msg16651.html

Regards,

Fabio Estevam