linux-kernel - Re: [PATCH v7 2/3] Documentation: dt: binding: fsl: Add 'little-endian' and update Chassis define

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Date:   Thu, 24 Oct 2019 13:33:45 -0500
From:   Scott Wood <oss@...error.net>
To:     Ran Wang <ran.wang_1@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Rob Herring <robh+dt@...nel.org>, Li Yang <leoyang.li@....com>,
        Mark Rutland <mark.rutland@....com>,
        Pavel Machek <pavel@....cz>
Cc:     Li Biwen <biwen.li@....com>, Len Brown <len.brown@...el.com>,
        devicetree@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7 2/3] Documentation: dt: binding: fsl: Add
 'little-endian' and update Chassis define

On Mon, 2019-10-21 at 11:49 +0800, Ran Wang wrote:
> By default, QorIQ SoC's RCPM register block is Big Endian. But
> there are some exceptions, such as LS1088A and LS2088A, are
> Little Endian. So add this optional property to help identify
> them.
> 
> Actually LS2021A and other Layerscapes won't totally follow Chassis
> 2.1, so separate them from powerpc SoC.

Did you mean LS1021A and "don't" instead of "won't", given the change to the
examples?

> Change in v5:
> 	- Add 'Reviewed-by: Rob Herring <robh@...nel.org>' to commit message.
> 	- Rename property 'fsl,#rcpm-wakeup-cells' to '#fsl,rcpm-wakeup-
> cells'.
> 	please see https://lore.kernel.org/patchwork/patch/1101022/

I'm not sure why Rob considers this the "correct form" -- there are other
examples of the current form, such as ibm,#dma-address-cells and ti,#tlb-
entries, and the current form makes more logical sense (# is part of the
property name, not the vendor).  Oh well.

> Required properites:
>    - reg : Offset and length of the register set of the RCPM block.
> -  - fsl,#rcpm-wakeup-cells : The number of IPPDEXPCR register cells in the
> +  - #fsl,rcpm-wakeup-cells : The number of IPPDEXPCR register cells in the
>  	fsl,rcpm-wakeup property.
>    - compatible : Must contain a chip-specific RCPM block compatible string
>  	and (if applicable) may contain a chassis-version RCPM compatible
> @@ -20,6 +20,7 @@ Required properites:
>  	* "fsl,qoriq-rcpm-1.0": for chassis 1.0 rcpm
>  	* "fsl,qoriq-rcpm-2.0": for chassis 2.0 rcpm
>  	* "fsl,qoriq-rcpm-2.1": for chassis 2.1 rcpm
> +	* "fsl,qoriq-rcpm-2.1+": for chassis 2.1+ rcpm

Is there something actually called "2.1+"?  It looks a bit like an attempt to
claim compatibility with all future versions.  If the former, is it a name
that comes from the hardware side with an intent for it to describe a stable
interface, or are we later going to see a patch changing some by-then-existing 
device trees from "2.1+" to "2.1++" when some new incompatibility is found?

Perhaps it would be better to bind to the specific chip compatibles.

-Scott