Re: [PATCH 1/2] slimbus: ngd: dt-bindings: Add slim ngd dt bindings

[Srinivas Kandagatla]

On 23/05/18 20:28, Rob Herring wrote:
> On Wed, May 23, 2018 at 1:11 PM, Srinivas Kandagatla
> <srinivas.kandagatla@xxxxxxxxxx> wrote:
> > On 23/05/18 17:40, Rob Herring wrote:
> > > > +
> > > > +- qcom,ngd-id
> > > > +       Usage: required
> > > > +       Value type: <u32>
> > > > +       Definition: ngd instance id in the controller
> > >
> > > Why do you need this?
> > Please ignore my comment from previous reply.
> >
> > There are more than one instances of ngd in this slim controller.
> > We need this to make sure we are programming the correct one.
>
> Doesn't the parent-child relationship of devices on the bus provide
> that? 
Thanks for the hint, that sounds like the actual problem here,
If I represent the node with proper parent-child relationship like this, 
it will remove the need of this property and would work perfectly in 
case we want to support multiple ngds in future!

slim@91c0000 {
	compatible = "qcom,msm8996-slim";
	reg = <0x91c0000 0x2C000>;
	interrupts = <0 163 0>;
	dmas = <&slimbam 3>, <&slimbam 4>;
	dma-names = "rx", "tx";
	#address-cells = <1>;
	#size-cells = <1>;
	ngd@1 {
		reg  = <1>;
		#address-cells = <1>;
		#size-cells = <1>;
		codec@1 {
			compatible = "slim217,1a0";
			reg  = <1 0>;
		};	
	};
};



If you mean to provide consistent numbering to userspace, then
> that's not a DT problem (nor one that Linux plans to solve).
No, this is not problem am trying to solve.

> > We also need this instance ID during powering it up using QMI.
>
> Wouldn't that be a QMI ID?

It is passed as parameter to SLIMBUS_QMI_SELECT_INSTANCE_REQ_V01 request.

thanks,
srini
> Rob