Re: [PATCH v2 3/4] arm64: dts: ti: k3-am67a-beagley-ai: Add overlay for IMX219 on CSI0

[Andrew Davis <afd@ti.com>]

On 5/29/26 10:01 AM, Nishanth Menon wrote:
> On 06:46-20260515, Jai Luthra wrote:
>> RPi v2 Camera (IMX219) is an 8MP camera that can be used with BeagleY AI
>> through the 22-pin CSI-RX connectors. Add a DT overlay to enable use of
>> this camera sensor through the CSI0 connector.
>>
>> Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
>> ---
>>   arch/arm64/boot/dts/ti/Makefile                    |   4 +
>>   .../dts/ti/k3-am67a-beagley-ai-csi0-imx219.dtso    | 121 +++++++++++++++++++++
> 
> Oh man..
> https://lore.kernel.org/linux-arm-kernel/20240702164403.29067-1-afd@ti.com/
> comes to memory.. Afd - what ever happened to that?
> 

Good question, others have taken over the torch for the most part. Nice
little talk[0] I found on some current status updates for the topic.

They even mention my little proof of concept around the 19min mark :D but
kinda just dismiss it as it doesn't support hotplug, which is a requirement
for their usecase. But my solution doesn't support hotplug because DT
doesn't support hotplug. And to add that kind of support to DT they are
pushing to change the DTC[1], the FDT format[2] (which hasn't changed in 19
years and is the basis for claiming DT is a firmware/"ABI"), and make an
alternative to DT overlays called "addon DTs"..

What I proposed was something that can work today without any changes
to existing DT infra. My only goal being to prevent needless duplication
in overlays like we see here where you have a new overlay for each
connector the device could be connected to. Just look at our evil vendor
tree to see what this problem can look like, go here[3] and search "fpdlink".
We have 14(!) overlays for just one camera sensor (IMX390) with the only
difference between each being a single line to select the FPD-Link port
where the sensor is connected.

Jai, I see you have already posted v3 of this series, but could you take
a look at what I've proposed here[4] and see if this could be used to make
a single IMX219 overlay that would work for both CSI ports? If you can
pull that off then we avoid the combinatorial explosion of an overlay
for each port on each board for each camera sensor.

Andrew

[0] https://www.youtube.com/watch?v=C8dEQ4OzMnc
[1] https://lore.kernel.org/devicetree-compiler/20260112142009.1006236-1-herve.codina@bootlin.com/
[2] https://lore.kernel.org/devicetree-compiler/20260409115426.352214-1-herve.codina@bootlin.com/
[3] https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti?h=ti-linux-6.18.y
[4] https://lore.kernel.org/linux-arm-kernel/20240702164403.29067-1-afd@ti.com/

> other than the dsi mux, painful to see so much duplication..
> 
> Other than that, there is the previous comment (ordering etc, repeated
> here). I also suggest people put the url of the board/part that the
> overlay is supposed to refer to when creating overlays.. at least, some
> sort of canonical link so folks are'nt confused in a future date.
> 
>