linux-kernel - Re: [RESEND] [PATCH v2 2/4] dt-bindings: Add jdi lt070me05000 panel bindings

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Message-ID: <CAGWqDJ6HuoHP5ygEG-SWUhaUqOjnzTCZb=xyO_pu8xXXHnq5Aw@mail.gmail.com>
Date:   Wed, 24 Aug 2016 17:53:00 +0530
From:   Vinay Simha <simhavcs@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Archit Taneja <archit.taneja@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND] [PATCH v2 2/4] dt-bindings: Add jdi lt070me05000 panel bindings

if we do not set the polarity to 8mA, panel will have gibberish display.
(information to set 8mA is available only in
nexus7-msm-flo-3.4-lollipop-release_dsi kernel nx7 release)

i will add this
reset-gpios = <&tlmm_pinmux 54 GPIO_ACTIVE_LOW>;

On Wed, Aug 24, 2016 at 5:26 PM, Thierry Reding
<thierry.reding@...il.com> wrote:
> On Sun, Jul 31, 2016 at 08:45:21PM +0530, Vinay Simha BN wrote:
> [...]
>> diff --git a/Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt b/Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt
> [...]
>> +- reset-gpios: phandle of gpio for reset line
>> +  This should be 8mA, gpio can be configured using mux, pinctrl, pinctrl-names
>> +  XRES, Reset, Low active
>> +- enable-gpios: phandle of gpio for enable line
>> +  LED_EN, LED backlight enable, High active
>
> This is a little confusing. Shouldn't we rather completely omit any
> mention of the polarity of these and let the board design handle this?
>
> If the reset is low active, then I'd expect that to be reflected in the
> GPIO specifier of the reset-gpios property, like so:
>
>         panel@0 {
>                 ...
>                 reset-gpios = <&tlmm_pinmux 54 GPIO_ACTIVE_LOW>;
>                 ...
>         };
>
> With that a driver can simply deal with a high active reset, which it
> currently doesn't. The problem with the current description is that it
> is unclear who's to deal with the polarity. In order for this to work
> properly with the current driver you'll have to specify the GPIO as
> GPIO_ACTIVE_HIGH, which is not what the binding says it should be.
>
> Thierry



-- 
regards,
vinaysimha