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

[Vikas Sajjan <vikas.sajjan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

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HI Tomasz,


On 10 May 2013 13:03, Tomasz Figa <tomasz.figa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> > > Hi Olof,
> > >
> > > On 10 May 2013 11:08, Olof Johansson <olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org> wrote:
> > >> On Thu, May 9, 2013 at 7:55 PM, Vikas Sajjan
> > >> <vikas.sajjan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > >>
> > >> wrote:
> > >> > Hi Tomasz,
> > >> >
> > >> > On 10 May 2013 05:35, Tomasz Figa <tomasz.figa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.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@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.

Best regards,
> Tomasz
>
>


-- 
Thanks and Regards
 Vikas Sajjan

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