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

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Message-ID: <47e022f4-1c1b-43c4-8f6c-bc1ff23ad39f@collabora.com>
Date: Wed, 5 Mar 2025 12:09:46 +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 12:03, Dmitry Osipenko wrote:
> 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.

BTW, I don't see it as a blocker. Driver works in general, new issues
can be resolved with additional patches.

-- 
Best regards,
Dmitry