Quoting Geert Uytterhoeven (2015-08-04 05:34:06)
> On Tue, Aug 4, 2015 at 2:22 PM, Laurent Pinchart
> <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
> > On Monday 03 August 2015 01:53:23 Kuninori Morimoto wrote:
> >> --- /dev/null
> >> +++ b/arch/arm64/boot/dts/renesas/r8a7795.dtsi
> >> @@ -0,0 +1,93 @@
> >> +/ {
>
> >> + clocks {
> >
> > Let's try to make it right from the start on Gen3. The CPG node should be a
> > direct child of the bus node mentioned above, and the MSTP clocks should be
> > children of the CPG node.
>
> Agreed.
>
> > I'm not sure where to put the non-memory-mapped clocks though, should they be
> > directly under the root node ? It would make sense for extal_clk, but how
> > about the fixed-factor clocks ? Should they be children of the CPG node too ?
>
> I believe the current trend is to put clocks like "extal_clk" under the root
> node.
> As the fixed-factor clocks are generated by the CPG module, and we do have
> a device node for it, I'd make them children of the CPG node, too.
>
> Any comments from the clk+dt experts?
I don't know if anyone is an expert ;-)
extal_clk should be under the root node. That is true for all
board-level clocks and clock controllers.
Within the SoC we want to model the clock controller as a node in DT,
not necessarily all of the individual clocks. So you definitely need a
"cpg" node in DT with #clock-cells > 0.
Whether or not you enumerate the individual clocks in DT is up to you. I
do not like the data-driven approach of putting the clock definition
data into DT. It makes it awkward to do things like set a flag on a
single clock later on. Simply using the clock controller phandle plus
one or more offsets is preferred over a per-clock phandle.
Stephen and I have been discussing what a formal clock-controller
binding would look like, and one item we came up with is that any
sub-nodes of the controller would not be allowed to have a #clock-cells
property.
Also, while you're thinking about the perfect clock binding, please do
consider dropping clock-output-names if you can. Specifying clock-names
alongside the clocks property inside of the consumer node is a bit more
elegant in my opinion. This is also a bit easier if you think about
expressing your clock data with C inside of your provider driver.
Regards,
Mike
>
> Thanks!
>
> >> + #address-cells = <2>;
> >> + #size-cells = <2>;
> >> + ranges;
> >> +
> >> + extal_clk: extal_clk {
> >> + compatible = "fixed-clock";
> >> + #clock-cells = <0>;
> >> + clock-frequency = <0>;
> >> + clock-output-names = "extal";
> >> + };
> >> + cpg_clocks: cpg_clocks@e6150000 {
> >> + compatible = "renesas,r8a7795-cpg-clocks",
> >> + "renesas,rcar-gen3-cpg-clocks";
> >> + reg = <0 0xe6150000 0 0x1000>;
> >> + clocks = <&extal_clk>;
> >> + #clock-cells = <1>;
> >> + clock-output-names = "main", "pll0", "pll1","pll2",
> >> + "pll3", "pll4";
> >> + };
> >> + p_clk: p_clk {
> >> + compatible = "fixed-factor-clock";
> >> + clocks = <&cpg_clocks RCAR_GEN3_CLK_PLL1>;
> >> + #clock-cells = <0>;
> >> + clock-div = <24>;
> >> + clock-mult = <1>;
> >> + clock-output-names = "p";
> >> + };
> >> + mstp3_clks: mstp3_clks@e615013c {
> >> + compatible = "renesas,r8a7795-mstp-clocks",
> >> + "renesas,cpg-mstp-clocks";
> >> + reg = <0 0xe615013c 0 4>, <0 0xe6150048 0 4>;
> >> + clocks = <&p_clk>;
> >> + #clock-cells = <1>;
> >> + renesas,clock-indices = <RCAR_GEN3_CLK_IRDA>;
> >> + clock-output-names = "irda";
> >> + };
> >> + };
> >> +};
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
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