linux-kernel - Re: [PATCH 1/2] dt-bindings: analogix-dp: Add backlight-pwm-passthru

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Date:   Sun, 18 Mar 2018 07:52:45 -0500
From:   Rob Herring <robh@...nel.org>
To:     Archit Taneja <architt@...eaurora.org>
Cc:     Alexandru M Stan <amstan@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Mark Rutland <mark.rutland@....com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Sean Paul <seanpaul@...omium.org>, devicetree@...r.kernel.org,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Heiko Stuebner <heiko@...ech.de>, briannorris@...omium.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        dianders@...omium.org, linux-rockchip@...ts.infradead.org,
        marcheu@...omium.org, hoegsberg@...omium.org,
        Thierry Escande <thierry.escande@...labora.com>,
        Jeffy Chen <jeffy.chen@...k-chips.com>
Subject: Re: [PATCH 1/2] dt-bindings: analogix-dp: Add backlight-pwm-passthru

On Fri, Mar 16, 2018 at 02:56:09PM +0530, Archit Taneja wrote:
> 
> 
> On Friday 16 March 2018 08:26 AM, Alexandru M Stan wrote:
> > Documentation for the optional backlight-pwm-passthru property.
> > Tells the EDP panel to folow the input pwm frequency instead
> 
> s/folow/follow
> 
> It would be nice if we could add the details you mentioned in
> patch #0 in either this or the next patch.
> 
> > of generating its own.
> 
> This is one of those bindings which is more a knob than a HW property,
> but I can't think of any easy way to figure this out in SW. So, I guess
> it's okay to have.
> 
> One thing I was wondering about was whether this prop should belong to
> the eDP controller or the eDP panel. I don't have any strong opinion
> about it, though.

Seems to me, it should be the panel. It's a setting in the panel, right?

Is this generic to DP panels or something specific to a certain panel? 
The naming (vendor prefix or not) and doc location should match 
whatever the answer to that is.

> 
> Reviewed-by: Archit Taneja <architt@...eaurora.org>
> 
> Thanks,
> Archit
> 
> 
> > 
> > Signed-off-by: Alexandru M Stan <amstan@...omium.org>
> > ---
> > 
> >   Documentation/devicetree/bindings/display/bridge/analogix_dp.txt | 4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/display/bridge/analogix_dp.txt b/Documentation/devicetree/bindings/display/bridge/analogix_dp.txt
> > index 0c7473dd0e51..3c15242f6ce3 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/analogix_dp.txt
> > +++ b/Documentation/devicetree/bindings/display/bridge/analogix_dp.txt
> > @@ -23,6 +23,10 @@ Required properties for dp-controller:
> >   		from general PHY binding: Should be "dp".
> >   Optional properties for dp-controller:
> > +	-backlight-pwm-passthru:
> > +		Directly pass the PWM frequency applied to the BL_PWM_DIM
> > +		pin to the backlight current source. Done via
> > +		EDP_BACKLIGHT_MODE_SET_REGISTER on DPCD.
> >   	-force-hpd:
> >   		Indicate driver need force hpd when hpd detect failed, this
> >   		is used for some eDP screen which don't have hpd signal.
> >