[PATCH 1/3] mmc: add support for power-on sequencing through DT

[Fabio Estevam]

On Mon, Jan 20, 2014 at 2:48 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> 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...

Isn't this covered by the gpios property of fixed-clock?

We do the following to enable the 26MHz codec clock in
imx51-babbage.dts via GPIO4_26:

        clk_26M: codec_clock {
            compatible = "fixed-clock";
            reg=<0>;
            #clock-cells = <0>;
            clock-frequency = <26000000>;
            gpios = <&gpio4 26 GPIO_ACTIVE_LOW>;
        };

Regards,

Fabio Estevam