[PATCH] ARM: tegra: Define Tegra20 CAR binding

[Stephen Warren]

Olof Johansson wrote at Saturday, January 21, 2012 12:32 AM:
> On Thu, Jan 19, 2012 at 9:17 AM, Stephen Warren <swarren at nvidia.com> wrote:
> > Olof Johansson wrote at Wednesday, January 18, 2012 10:32 PM:
> >> On Wed, Jan 18, 2012 at 05:16:52PM -0700, Stephen Warren wrote:
> >> > diff --git a/Documentation/devicetree/bindings/clock/nvidia,tegra20-car.txt
> >> > +* NVIDIA Tegra20 Clock And Reset Controller
> >> > +
> >> > +This binding uses the common clock binding:
> >> > +Documentation/devicetree/bindings/clock/clock-bindings.txt
> >> > +
> >> > +The CAR (Clock And Reset) Controller on Tegra is the HW module responsible
> >> > +for muxing and gating Tegra's clocks, and setting their rates.
> >> > +
> >> > +Required properties :
> >> > +- compatible : Should be "nvidia,<chip>-car"
> >> > +- reg : Should contain CAR registers location and length
> >> > +- clocks : Should contain phandle and clock specifiers for two clocks:
> >> > +  the 32 KHz "32k_in", and the board-specific oscillator "osc".
> >> > +- clock-names : Should contain a list of strings, with values "32k_in",
> >> > +  and "osc".
...
> >> > +Example:
> >> > +
> >> > +clocks {
> >> > +   clk_32k: oscillator at 0 {
> >>
> >> If it has a unit addres (@<x>) it needs a reg property with the same base
> >> address.
> >
> > I thought everything needed a unit address period? Is the rule more like
> > the unit address is optional, but if present must match reg, so I can
> > simply remove @0 and @1 here? I guess that makes a lot more sense.
> 
> Nope, you only need a unit address to make a node unique, i.e. if you
> have more than one with the same name. It's not something that's been
> followed very well on ARM dts files, I have even seen review comments
> asking for explicit unit IDs when none are needed.
> 
> So you can't remove @0 and @1 here, since there are two oscillator subnodes.

If I keep the unit address, then I need to add a reg property per Mitch's
response. But, then I need #address-cells and #size-cells in the clock
node too. Yuck, since this isn't an addressable bus.

Instead, is it acceptable to simply rename the nodes to e.g.:

clk_32k: clock {...};
osc: crystal {...};

In the long term, I believe that osc/crystal is going to continue to
be a top-level object, but clk_32k is actually an output from the PMU
chip, and hence there won't be any naming conflict here anyway...

-- 
nvpublic