[alsa-devel] ASoC: new ac97 bus and codec clock

[Robert Jarzmik]

Rob Herring <robh+dt at kernel.org> writes:

> Like PCI, USB, SDIO, etc., you need to define an AC97 bus binding
> which defines child node structure, compatible formatting (if you can
> base compatibles on something like VID/PID), and addressing (reg and
> unit-address formats). Then once you define child nodes, you can add
> whatever sideband connections you need. The AC97 core should be able
> to populate struct device_node if there are any matching child
> devices.
Ok, I thing I understand.

So the device-tree will look like :
ac97: sound at 40500000 {
      	compatible = "marvell,pxa270-ac97";
	reg = < 0x40500000 0x1000 >;
	interrupts = <14>;
	reset-gpios = <&gpio 95 GPIO_ACTIVE_HIGH>;
	#sound-dai-cells = <1>;
	pinctrl-names = "default";
	pinctrl-0 = < &pinctrl_ac97_default >;
	clocks = <&clks CLK_AC97>, <&clks CLK_AC97CONF>;
	clock-names = "AC97CLK", "AC97CONFCLK";

        wm9713 at 0 {
        	reg = <0>; /* Codex index (between 0 and 3) */
                compatible = "ac97-codec";
                clocks = <&fixed_wm9713_clock>;
                clock-names = "ac97_clk";
        }
};

And the function ac97_codec_add() will :
 - scan the device-tree ac97 controller childs
 - match one if its reg equals (in our case wm9713 at 0)
 - set codec->dev.of_node to the matched one

> It gets a bit more complicated if you need to do things like
> enable power or de-assert resets to discover the devices. Sounds like
> that might be the next person's problem in this case. :)
Yeah ... Crossing fingers that won't be me :)

Cheers.

-- 
Robert