[PATCH 2/7] of: add clock providers

[Shawn Guo]

On Mon, Apr 09, 2012 at 08:52:35AM -0500, Rob Herring wrote:
> On 04/09/2012 06:55 AM, Shawn Guo wrote:
> > On Tue, Mar 13, 2012 at 06:22:22PM -0500, Rob Herring wrote:
> > ...
> >> +==Clock consumers==
> >> +
> >> +Required properties:
> >> +clocks:		List of phandle and clock specifier pairs, one pair
> >> +		for each clock input to the device.  Note: if the
> >> +		clock provider specifies '0' for #clock-cells, then
> >> +		only the phandle portion of the pair will appear.
> > 
> > Per discussion[1], the parent of the clock could be reasonably
> > represented in C code instead of in device tree.  Then how can
> > this "clocks" property be "Required"?  Or to put it another way,
> > if this is "Required", the whole clock tree will have to be represented
> > in device tree, no?
> > 
> 
> I'm not sure I follow. All of this only applies if you are doing clock
> setup from DT. Whether you represent all clocks or only the outputs to
> devices in DT is up to you. So you could have a CCM node for imx with 50
> clock outputs and all the intermediate clocks within the CCM are
> represented with C code.
> 
Ok, now I have uart clock being one of the 50 clocks represented in
device tree, while the parent of uart clock ipg_per is represented in
C code.  That said, I do not have a ipg_per clock node in device tree.
My question is how I should give that required "clocks" property for
the uart clock node.

	uart_serial_clk: uart-baud {
		compatible = "fsl,imx6q-clock";
		#clock-cells = <0>;
		/* clocks = <&ipg_per_clk>; */
		clocks = <???>;
	};

	uart: serial at 02020000 {
		compatible = "fsl,imx6q-uart", "fsl,imx21-uart";
		reg = <0x02020000 0x4000>;
		interrupts = <0 26 0x04>;
		clocks = <&uart_serial_clk>
	}

Regards,
Shawn

> In other words, at minimum you are just replacing the clkdev lookup with
> a DT lookup.
>