[PATCH 3/3] ARM: dts: Add display timing node to exynos5250-arndale.dts

[Vikas Sajjan]

Hi Steffen Trumtrar and Sascha Hauer,

Olof and Tomasz Figa have a concern in putting "display-timings"  as root
node in device tree file.


On 10 May 2013 13:45, Vikas Sajjan <vikas.sajjan at linaro.org> wrote:

> HI Tomasz,
>
>
> On 10 May 2013 13:03, Tomasz Figa <tomasz.figa at gmail.com> wrote:
>
>> On Friday 10 of May 2013 11:57:34 Vikas Sajjan wrote:
>> > Hi Olof,
>> >
>> > On 10 May 2013 11:51, Vikas Sajjan <vikas.sajjan at linaro.org> wrote:
>> > > Hi Olof,
>> > >
>> > > On 10 May 2013 11:08, Olof Johansson <olof at lixom.net> wrote:
>> > >> On Thu, May 9, 2013 at 7:55 PM, Vikas Sajjan
>> > >> <vikas.sajjan at linaro.org>
>> > >>
>> > >> wrote:
>> > >> > Hi Tomasz,
>> > >> >
>> > >> > On 10 May 2013 05:35, Tomasz Figa <tomasz.figa at gmail.com> wrote:
>> > >> >> Hi Vikas,
>> > >> >>
>> > >> >> On Wednesday 08 of May 2013 11:31:34 Vikas Sajjan wrote:
>> > >> >> > Adds display timing node for a DP panel to Arndale Board DTS
>> > >> >> > file
>> > >> >> >
>> > >> >> > Signed-off-by: Vikas Sajjan <vikas.sajjan at linaro.org>
>> > >> >> > ---
>> > >> >> >
>> > >> >> >  arch/arm/boot/dts/exynos5250-arndale.dts |   16
>> > >> >> >  ++++++++++++++++
>> > >> >> >  1 file changed, 16 insertions(+)
>> > >> >> >
>> > >> >> > diff --git a/arch/arm/boot/dts/exynos5250-arndale.dts
>> > >> >> > b/arch/arm/boot/dts/exynos5250-arndale.dts index
>> > >> >> > f68b820..c831a5c
>> > >> >> > 100644
>> > >> >> > --- a/arch/arm/boot/dts/exynos5250-arndale.dts
>> > >> >> > +++ b/arch/arm/boot/dts/exynos5250-arndale.dts
>> > >> >> > @@ -459,4 +459,20 @@
>> > >> >> >
>> > >> >> >               samsung,lane-count = <4>;
>> > >> >> >
>> > >> >> >       };
>> > >> >> >
>> > >> >> > +     display-timings {
>> > >> >> > +             native-mode = <&timing0>;
>> > >> >> > +             timing0: timing at 0 {
>> > >> >> > +                     /* 2560x1600 DP panel */
>> > >> >> > +                     clock-frequency = <50000>;
>> > >> >> > +                     hactive = <2560>;
>> > >> >> > +                     vactive = <1600>;
>> > >> >> > +                     hfront-porch = <48>;
>> > >> >> > +                     hback-porch = <80>;
>> > >> >> > +                     hsync-len = <32>;
>> > >> >> > +                     vback-porch = <16>;
>> > >> >> > +                     vfront-porch = <8>;
>> > >> >> > +                     vsync-len = <6>;
>> > >> >> > +             };
>> > >> >> > +     };
>> > >> >>
>> > >> >> What display are those timings used for? Shouldn't they be placed
>> > >>
>> > >> inside
>> > >>
>> > >> >> node of that display?
>> > >> >
>> > >> > This timing information will be used parsed by the FIMD probe with
>> > >> > the
>> > >>
>> > >> help
>> > >>
>> > >> > of "Video Helper function"  as done in this link
>> > >>
>> > >>
>> https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-exynos.git/c
>> > >> ommit/?h=exynos-drm-next&id=7f4596f4aebcc9fcf2d50d3fe398508d710c4dd0
>> > >>
>> > >> That function passes in a device node pointer to the FIMD device
>> > >> node,
>> > >> and only looks for a display-timings node under there. Tomasz is
>> > >> right, as far as I can tell.
>> > >>
>> > >> Placing display timings at the root of the device tree seems
>> > >> completely
>> > >> wrong.
>> > >>
>> > >>         I referred this "
>> >
>> > Documentation/devicetree/bindings/video/display-timing.txt" for example
>> >
>> >             here it dosen't mention about whether display timings node
>> > can be placed at the root of the device tree or NOT.
>> >  Not sure how we should be placing the node then.
>>
>> I think this is pretty obvious.
>>
>> Imagine a bit more complex case: a board has two video outputs (let's say
>> FIMD0 and FIMD1), each connected to a completely different display. This
>> means that each display needs different timings.
>>
>> How would you know which timings to use if all of them were be placed
>> under the root node?
>>
>>     so what do you think, how  should we modify this patch so that it
> belongs to a specific video outputs.
>
>

  So what do you think, how should we modify this patch so that it belongs
to a specific video outputs.




>  Best regards,
>> Tomasz
>>
>>
>
>
> --
> Thanks and Regards
>  Vikas Sajjan
>



-- 
Thanks and Regards
 Vikas Sajjan
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