linux-kernel - Re: [PATCH v13 0/6] Add Synopsys DesignWare HDMI RX Controller

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Message-ID: <88054acf-3051-414c-aef7-4c0f085d5182@collabora.com>
Date: Wed, 5 Mar 2025 12:03:33 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: Hans Verkuil <hverkuil@...all.nl>, Tim Surber <me@...surber.de>,
 Shreeya Patel <shreeya.patel@...labora.com>, Heiko Stuebner
 <heiko@...ech.de>, Mauro Carvalho Chehab <mchehab@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, jose.abreu@...opsys.com,
 nelson.costa@...opsys.com, shawn.wen@...k-chips.com,
 nicolas.dufresne@...labora.com,
 Sebastian Reichel <sebastian.reichel@...labora.com>
Cc: kernel@...labora.com, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-rockchip@...ts.infradead.org,
 Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Diederik de Haas <didi.debian@...ow.org>
Subject: Re: [PATCH v13 0/6] Add Synopsys DesignWare HDMI RX Controller

On 3/5/25 11:10, Hans Verkuil wrote:
> On 05/03/2025 01:59, Tim Surber wrote:
>> Hi Dmitry,
>>
>> I did some more testing. That the Apple TV did not work was a bit 
>> misleading.
>>
>> It was just, that the Apple TV defaulted to 4:4:4 Chroma which does not 
>> work at all for me. (The same happens using the vendor driver).
>>
>> When I changed the EDID to match the vendor driver the HDMI handshake 
>> happened with 4:2:0 chroma, where I could verify even 4k60fps using your 
>> driver, nice!
>>
>> So the remaining problems I see are:
>> - 4:4:4 chroma not working in any resolution
>> - 4:2:2 and RGB not working in 4k60fps (is this a hardware limitation?)
>>
>> A possible workaround could be to disable these non supported formats in 
>> the default EDID.
> I would like to merge this driver this week, since otherwise it will likely
> slip to v6.16. So if there is a working EDID, perhaps it can be used for now,
> and later on it can be patched if there is a better EDID.
> 
> Would this EDID work? Tim, can you try this?
> 
> v4l2-ctl --set-edid type=hdmi-4k-600mhz,ycbcr444,ycbcr422
> 
> Alternatively, if there is indeed a HW limitation that prevents 4kp60 to work,
> try this:
> 
> v4l2-ctl --set-edid type=hdmi-4k-300mhz,ycbcr444,ycbcr422
> 
> Whichever of the two works is what we can use as default EDID.

Disabling 444 and 422 is an option. Though, they work on my setup at
4k@....

In general, it often a challenge to get 4k@60p properly with any of
these small board devices. 4k@60p works only using a short HDMI cable
for me. Also, not everyone aware that the micro HDMI adapter needs to be
compliant with HDMI 2.0 for 4k@60, that's why 300MHz is the default.

Will be nice to have the good EDID enabled by default in the defconfig.
Dealing with problems like that will be a headache for majority of
people, IMO.

-- 
Best regards,
Dmitry