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Subject: Re: [PATCH v16 4/4] drm/bridge: dw-hdmi: fix bus formats negotiation
 for 8 bit modes
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <890BB299-AB92-4177-83E8-74C8AA551AF1@goldelico.com>
Date:   Thu, 3 Mar 2022 16:37:06 +0100
Cc:     Paul Boddie <paul@boddie.org.uk>, Jonas Karlman <jonas@kwiboo.se>,
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        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Discussions about the Letux Kernel 
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To:     Neil Armstrong <narmstrong@baylibre.com>
Precedence: bulk

Hi Neil,

> Am 03.03.2022 um 12:45 schrieb H. Nikolaus Schaller =
<hns@goldelico.com>:
>=20
> Hi Neil,
>=20
>> Am 03.03.2022 um 12:42 schrieb Neil Armstrong =
<narmstrong@baylibre.com>:
>>=20
>>> So how can we get that merged? IMHO your proposal should be before =
we add ingenic-dw-hdmi.
>>> If you have a version with proper commit message I can add it to the =
beginning of my
>>> seried and include it in a v17. Or if you get yours merged to =
drm-misc/drm-misc-next I
>>> can build on top.
>>=20
>> You can add it in your v17 patchset with my authorship and my =
Signed-off-by tag + yours.
>>=20
>> As commit message something like :
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>> drm/bridge: dw-hdmi: handle unusable or non-configured CSC module
>>=20
>> The dw-hdmi integrates an optional Color Space Conversion feature =
used
>> to handle color-space conversions.
>>=20
>> On some platforms, the CSC isn't built-in or non-functional.
>>=20
>> This adds the necessary code to disable the CSC functionality
>> and limit the bus format negotiation to force using the same
>> input bus format as the output bus format.
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>=20
> Fine! Will do.

I was a little too early.

While preparing the patches I found that I still had the hack to force
sink_is_hdmi =3D false in my test branch. Sorry for that.

Removing this made the panel go black again, even with your latest
proposal.

So I looked deeper into your patch and it seems to influence the
input formats only in dw_hdmi_bridge_atomic_get_input_bus_fmts()?

While the problem I see is with output formats and we had worked on
modifying dw_hdmi_bridge_atomic_get_output_bus_fmts().

BR and thanks,
Nikolaus