linux-kernel - Re: [PATCH v5 2/2] arm64: dts: qcom: talos-evk: Add support for QCS615 talos evk board

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Message-ID: <1e13b14a-83eb-4ab3-b5e3-4721a6026b65@gmail.com>
Date: Wed, 5 Nov 2025 18:23:32 +0530
From: Tessolve Upstream <tessolveupstream@...il.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, andersson@...nel.org,
 konradybcio@...nel.org
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] arm64: dts: qcom: talos-evk: Add support for
 QCS615 talos evk board



On 05/11/25 16:39, Konrad Dybcio wrote:
> On 11/5/25 11:01 AM, Tessolve Upstream wrote:
>>
>>
>> On 04/11/25 19:57, Konrad Dybcio wrote:
>>> On 11/4/25 1:51 PM, Sudarshan Shetty wrote:
>>>> Introduce the device tree support for the QCS615-based talos-evk
>>>> platform, which follows the SMARC (Smart Mobility ARChitecture)
>>>> standard. The platform is composed of two main hardware
>>>> components: the talos-evk-som and the talos-evk carrier board.
>>>
>>> How is the carrier board a separate entity from the "talos-evk.dts"?
>>
>> The talos-evk platform follows a modular SoM + carrier design.
>> In our current implementation:
>> talos-evk-som.dtsi — describes SoM-specific components.
>> talos-evk-cb.dtsi — represents the carrier board and includes the
>> SoM file, adding carrier-specific interfaces (micro SD, power button etc.).
>> talos-evk.dts — includes both the SoM and CB DTSIs and enables HDMI 
>> display configuration.
>> talos-evk-lvds.dts — also includes both the SoM and CB DTSIs but enables 
>> LVDS instead of HDMI.
>>
>> HDMI and LVDS share the same DSI output and cannot be used simultaneously.
>> Therefore, we provide separate top-level DTS files (talos-evk.dts for HDMI
>> and talos-evk-lvds.dts for LVDS), while keeping common board
>> logic in talos-evk-cb.dtsi.
>>
>> Hence, layer looks as below:
>>
>> talos-evk-som.dtsi
>> ├── talos-evk-cb.dtsi (includes som)
>> │    ├── talos-evk.dts (HDMI)
>> │    └── talos-evk-lvds.dts (LVDS)
>>
>> This ensures modularity, and properly models mutually exclusive display
>> configurations.
> 
> And are both the LVDS display and HDMI converter on separate add-in boards?
> 
Both HDMI and LVDS interfaces are present on the same carrier board, 
but they share the same DSI output from the SoM.

The hardware requires physical reconfiguration (resistor changes)
to select either the ADV7535 HDMI path or the LVDS bridge path.

Because they cannot be used simultaneously and represent different hardware
configurations, we provide two separate DTS files — one for HDMI and 
one for LVDS — while keeping the common carrier definitions in talos-evk-cb.dtsi.
> Konrad