Subject: Re: [PATCH net-next V2] dt-bindings: net: ethernet-controller: Add ptp-hardware-clock

From: Rob Herring <[email-masked]>
Date: Mon, 24 Oct 2022 11:57:23 -0500

On Thu, Oct 20, 2022 at 11:41:10PM -0600, Sarath Babu Naidu Gaddam wrote:
> There is currently no standard property to pass PTP device index
> information to ethernet driver when they are independent.
> 
> ptp-hardware-clock property will contain phandle to PTP clock node.
> 
> Freescale driver currently has this implementation but it will be
> good to agree on a generic (optional) property name to link to PTP
> phandle to Ethernet node. In future or any current ethernet driver
> wants to use this method of reading the PHC index,they can simply use
> this generic name and point their own PTP clock node, instead of
> creating separate property names in each ethernet driver DT node.

Seems like this does the same thing as 
Documentation/devicetree/bindings/ptp/timestamper.txt.

Or perhaps what we have in bindings/timestamp/ which unfortunately does 
about the same thing.

The latter one is more flexible and follows standard provider/consumer 
patterns. So timestamper.txt should probably be deprecated.

> 
> axiethernet driver uses this method when PTP support is integrated.
> 
> Example:
> 	fman0: fman@1a00000 {
> 		ptp-hardware-clock = <&ptp_timer0>;
> 	}
> 
> 	ptp_timer0: ptp-timer@1afe000 {
> 		compatible = "fsl,fman-ptp-timer";
> 		reg = <0x0 0x1afe000 0x0 0x1000>;
> 	}
> 
> Signed-off-by: Sarath Babu Naidu Gaddam <[email-masked]>
> ---
> We want binding to be reviewed/accepted and then make changes in freescale
> binding documentation to use this generic binding.

If you want a common binding, I want to see multiple users and 
preferrably ones that have some differing requirements. It can be 
something existing with a 'this is what it would look like if we had 
used this new common binding'.

Rob