linux-kernel - Re: [PATCH v6 1/3] dt-bindings: display: bridge: Document THC63LVD1024 LVDS decoder

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Message-ID: <20180327085748.GK27746@w540>
Date:   Tue, 27 Mar 2018 10:57:48 +0200
From:   jacopo mondi <jacopo@...ndi.org>
To:     Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Cc:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Rob Herring <robh@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        architt@...eaurora.org, airlied@...ux.ie, horms@...ge.net.au,
        magnus.damm@...il.com, geert@...ux-m68k.org,
        niklas.soderlund@...natech.se, mark.rutland@....com,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] dt-bindings: display: bridge: Document
 THC63LVD1024 LVDS decoder

Hi Vladimir,

On Tue, Mar 27, 2018 at 11:30:29AM +0300, Vladimir Zapolskiy wrote:
> Hi Sergei,
>
> On 03/27/2018 11:27 AM, Sergei Shtylyov wrote:
> > Hello!
> >
> > On 3/27/2018 10:33 AM, jacopo mondi wrote:
> > [...]
> >>>>>>> Document Thine THC63LVD1024 LVDS decoder device tree bindings.
> >>>>>>>
> >>>>>>> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> >>>>>>> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> >>>>>>> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
> >>>>>>> ---
> >>>>>>>   .../bindings/display/bridge/thine,thc63lvd1024.txt | 66 +++++++++++++++++++
> >>>>>>>   1 file changed, 66 insertions(+)
> >>>>>>>   create mode 100644
> >>>>>>> Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> >>>>>>>
> >>>>>>> diff --git
> >>>>>>> a/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> >>>>>>> b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> >>>>>>> new file mode 100644
> >>>>>>> index 0000000..8225c6a
> >>>>>>> --- /dev/null
> >>>>>>> +++
> >>>>>>> b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> >>>>>>> @@ -0,0 +1,66 @@
> >>>>>>> +Thine Electronics THC63LVD1024 LVDS decoder
> >>>>>>> +-------------------------------------------
> >>>>>>> +
> >>>>>>> +The THC63LVD1024 is a dual link LVDS receiver designed to convert LVDS
> >>>>>>> streams
> >>>>>>> +to parallel data outputs. The chip supports single/dual input/output modes,
> >>>>>>> +handling up to two two input LVDS stream and up to two digital CMOS/TTL
> >>>>>>> outputs.
> >>>>>>> +
> >>>>>>> +Single or dual operation modes, output data mapping and DDR output modes
> >>>>>>> are
> >>>>>>> +configured through input signals and the chip does not expose any control
> >>>>>>> bus.
> >>>>>>> +
> >>>>>>> +Required properties:
> >>>>>>> +- compatible: Shall be "thine,thc63lvd1024"
> >>>>>>> +
> >>>>>>> +Optional properties:
> >>>>>>> +- vcc-supply: Power supply for TTL output and digital circuitry
> >>>>>>> +- cvcc-supply: Power supply for TTL CLOCKOUT signal
> >>>>>>> +- lvcc-supply: Power supply for LVDS inputs
> >>>>>>> +- pvcc-supply: Power supply for PLL circuitry
> >>>>>> As explained in a comment to one of the previous versions of this series, I'm
> >>>>>> tempted to make vcc-supply mandatory and drop the three other power supplies
> >>>>>> for now, as I believe there's very little chance they will be connected to
> >>>>>> separately controllable regulators (all supplies use the same voltage). In the
> >>>>>> very unlikely event that this occurs in design we need to support in the
> >>>>>> future, the cvcc, lvcc and pvcc supplies can be added later as optional
> >>>>>> without breaking backward compatibility.
> >>>>> I'm okay with that.
> >>>>>
> >>>>>> Apart from that,
> >>>>>>
> >>>>>> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> >>>>>>
> >>>>>>> +- pdwn-gpios: Power down GPIO signal. Active low
> >>>>> powerdown-gpios is the semi-standard name.
> >>>>>
> >>>> right, I've also noticed it. If possible please avoid shortenings in
> >>>> property names.
> >>>
> >>> It is not shortening, it just follow pin name from decoder's datasheet.
> >>>
> >>>>
> >>>>>>> +- oe-gpios: Output enable GPIO signal. Active high
> >>>>>>> +
> >>>> And this one is also a not ever met property name, please consider to
> >>>> rename it to 'enable-gpios', for instance display panels define it.
> >>>
> >>>
> >>> Again, it follows datasheet naming scheme. Has something changed in DT
> >>> conventions?
> >>
> >> Seconded. My understanding is that the property name should reflect
> >> what reported in the the chip manual. For THC63LVD1024 the enable and
> >> power down pins are named 'OE' and 'PDWN' respectively.
> >
> >     But don't we need the vendor prefix in the prop names then, like
> > "renesas,oe-gpios" then?
> >
>
> Seconded, with a correction to "thine,oe-gpios".
>

mmm, okay then...

A grep for that semi-standard properties names in Documentation/
returns only usage examples and no actual definitions, so I assume this
is why they are semi-standard. Seems like there is some tribal knowledge
involved in defining what is semi-standard and what's not, or are those
properties documented somewhere?

Thanks
   j


> If vendor agnostic properties are supposed to be used, then please follow
> the referenced by Rob semi-standard notations.
>
> --
> With best wishes,
> Vladimir

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