Re: [PATCH v1 1/1] arm64: dts: qcom: talos-evk: Add support for dual-channel LVDS panel

[Tessolve Upstream <tessolveupstream@gmail.com>]

On 29/10/25 21:18, Bjorn Andersson wrote:
> On Tue, Oct 28, 2025 at 11:46:36AM +0530, Sudarshan Shetty wrote:
>> This patch introduces a new device tree for the QCS615 Talos
> 
> "This patch" doesn't make sense when you look at the git log once the
> patch has been accepted, please avoid it.
> 
> Please read https://docs.kernel.org/process/submitting-patches.html#describe-your-changes
> 
> Start your commit message with a "problem description", describe what
> this LVDS talos is, why it should have it's own dts file etc.

Okay, will update in next patch.
> 
>> EVK platform with dual-channel LVDS display support.
>>
>> The new DTS file (`talos-evk-lvds.dts`) is based on the existing
>> `talos-evk.dts` and extends it to enable a dual-channel LVDS display
>> configuration using the TI SN65DSI84 DSI-to-LVDS bridge.
>>
>> where channel-A carries odd pixel and channel-B carries even pixel
>> on the QCS615 talos evk platform.
>>
>> Signed-off-by: Sudarshan Shetty <tessolveupstream@gmail.com>
>> ---
>>  arch/arm64/boot/dts/qcom/Makefile           |   1 +
>>  arch/arm64/boot/dts/qcom/talos-evk-lvds.dts | 128 ++++++++++++++++++++
>>  2 files changed, 129 insertions(+)
>>  create mode 100644 arch/arm64/boot/dts/qcom/talos-evk-lvds.dts
>>
>> diff --git a/arch/arm64/boot/dts/qcom/Makefile b/arch/arm64/boot/dts/qcom/Makefile
>> index d5a3dd98137d..6e7b04e67287 100644
>> --- a/arch/arm64/boot/dts/qcom/Makefile
>> +++ b/arch/arm64/boot/dts/qcom/Makefile
>> @@ -307,6 +307,7 @@ dtb-$(CONFIG_ARCH_QCOM)	+= sm8750-mtp.dtb
>>  dtb-$(CONFIG_ARCH_QCOM)	+= sm8750-qrd.dtb
>>  dtb-$(CONFIG_ARCH_QCOM)	+= talos-evk.dtb
>>  dtb-$(CONFIG_ARCH_QCOM)	+= talos-evk-dsi.dtb
>> +dtb-$(CONFIG_ARCH_QCOM)	+= talos-evk-lvds.dtb
>>  x1e001de-devkit-el2-dtbs	:= x1e001de-devkit.dtb x1-el2.dtbo
>>  dtb-$(CONFIG_ARCH_QCOM)	+= x1e001de-devkit.dtb x1e001de-devkit-el2.dtb
>>  x1e78100-lenovo-thinkpad-t14s-el2-dtbs	:= x1e78100-lenovo-thinkpad-t14s.dtb x1-el2.dtbo
>> diff --git a/arch/arm64/boot/dts/qcom/talos-evk-lvds.dts b/arch/arm64/boot/dts/qcom/talos-evk-lvds.dts
>> new file mode 100644
>> index 000000000000..7ba4ab96ada6
>> --- /dev/null
>> +++ b/arch/arm64/boot/dts/qcom/talos-evk-lvds.dts
>> @@ -0,0 +1,128 @@
>> +// SPDX-License-Identifier: BSD-3-Clause
>> +/*
>> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
>> + */
>> +/dts-v1/;
>> +#include "talos-evk.dts"
> 
> We don't include .dts files, split the existing one in a dtsi and dts
> file and then include the dtsi here. Or provide provide this as a dtso
> overlay on top of the dts.
> 
> It's not clear to me which is the correct way, because you didn't
> adequately described how the SN65DSI84 enter the picture. Is it always
> there, but not part of the standard dip-switch configuration? Or is this
> some mezzanine?
> 
> Regards,
> Bjorn
> 

Thanks for the feedback.
Currently, the Talos device tree hierarchy is organized as follows:

talos-som.dtsi — defines SoM-specific interfaces
talos-evk.dts — adds carrier board (CB) interfaces such as MicroSD, power
button, and HDMI
talos-evk-lvds.dts — enables the LVDS display (includes SoM + CB +
LVDS + disables HDMI)

The LVDS and HDMI displays share a common DSI output, so only one 
interface can be active at a time. At present, talos-evk-lvds.dts 
includes talos-evk.dts directly so that the base SoM and carrier 
interfaces (e.g., MicroSD, power button) remain available.

However, as you pointed out, including a .dts file directly is not
recommended upstream. To address this, I am considering the following 
restructuring options:

Option 1: Introduce a talos-cb.dtsi

talos-som.dtsi: SoM-specific interfaces
talos-cb.dtsi: common carrier board interfaces (MicroSD, power button, etc.)
talos-evk.dts: includes talos-som.dtsi + talos-cb.dtsi + HDMI
talos-evk-lvds.dts: includes talos-som.dtsi + talos-cb.dtsi + LVDS

This approach avoids including .dts files directly and keeps the carrier
board interfaces centralized and reusable.It also cleanly separates SoM
and CB content and is consistent with how other Qualcomm platforms 
structure their EVK variants.

Option 2: Move CB interfaces to talos-som.dtsi (disabled by default)

Move MicroSD, power button, etc., to talos-som.dtsi with status = "disabled";
Enable these interfaces in each top-level DTS (e.g., talos-evk.dts,
talos-evk-lvds.dts)
While this also avoids .dts inclusion, it may make the SoM DTS 
unnecessarily complex and less reusable, as those CB-specific 
peripherals don’t belong to the SoM hardware.

Let me know your prepared approach here.
>> +
>> +/ {
>> +
>> +	backlight: backlight {
>> +		compatible = "gpio-backlight";
>> +		gpios = <&tlmm 115 GPIO_ACTIVE_HIGH>;
>> +		default-on;
>> +	};
>> +
>> +	lcd0_pwm_en {
>> +		compatible = "pwm-gpio";
>> +		gpios = <&tlmm 59 GPIO_ACTIVE_HIGH>;
>> +		pinctrl-0 = <&lcd0_bklt_pwm>;
>> +		pinctrl-names = "default";
>> +		#pwm-cells = <3>;
>> +	};
>> +
>> +	panel-lvds {
>> +		compatible = "auo,g133han01";
>> +
>> +		ports {
>> +			#address-cells = <1>;
>> +			#size-cells = <0>;
>> +
>> +			/* LVDS A (Odd pixels) */
>> +			port@0 {
>> +				reg = <0>;
>> +				dual-lvds-odd-pixels;
>> +
>> +				lvds_panel_out_a: endpoint {
>> +					remote-endpoint = <&sn65dsi84_out_a>;
>> +				};
>> +			};
>> +
>> +			/* LVDS B (Even pixels) */
>> +			port@1 {
>> +				reg = <1>;
>> +				dual-lvds-even-pixels;
>> +
>> +				lvds_panel_out_b: endpoint {
>> +					remote-endpoint = <&sn65dsi84_out_b>;
>> +				};
>> +			};
>> +		};
>> +	};
>> +};
>> +
>> +&adv7535 {
>> +	status = "disabled";
>> +};
>> +
>> +&i2c1 {
>> +	clock-frequency = <400000>;
>> +
>> +	status = "okay";
>> +
>> +	sn65dsi84: sn65dsi84@2c {
>> +		compatible = "ti,sn65dsi84";
>> +		reg = <0x2c>;
>> +		enable-gpios = <&tlmm 42 GPIO_ACTIVE_HIGH>;
>> +		ti,dsi-lanes = <4>;
>> +		ti,lvds-format = "jeida-24";
>> +		ti,lvds-bpp = <24>;
>> +
>> +		ports {
>> +			#address-cells = <1>;
>> +			#size-cells = <0>;
>> +
>> +			port@0 {
>> +				reg = <0>;
>> +
>> +				sn65dsi84_in: endpoint {
>> +					data-lanes = <0 1 2 3>;
>> +					remote-endpoint = <&mdss_dsi0_out>;
>> +				};
>> +			};
>> +
>> +			port@2 {
>> +				reg = <2>;
>> +
>> +				sn65dsi84_out_a: endpoint {
>> +					data-lanes = <0 1 2 3>;
>> +					remote-endpoint = <&lvds_panel_out_a>;
>> +				};
>> +			};
>> +
>> +			port@3 {
>> +				reg = <3>;
>> +
>> +				sn65dsi84_out_b: endpoint {
>> +					data-lanes = <0 1 2 3>;
>> +					remote-endpoint = <&lvds_panel_out_b>;
>> +				};
>> +			};
>> +		};
>> +	};
>> +};
>> +
>> +&mdss_dsi0 {
>> +	vdda-supply = <&vreg_l11a>;
>> +
>> +	status = "okay";
>> +};
>> +
>> +&mdss_dsi0_out {
>> +	remote-endpoint = <&sn65dsi84_in>;
>> +	data-lanes = <0 1 2 3>;
>> +};
>> +
>> +&tlmm {
>> +	lcd0_bklt_en: lcd0-bklt-en-state {
>> +		pins = "gpio115";
>> +		function = "gpio";
>> +		bias-disable;
>> +	};
>> +
>> +	lcd0_bklt_pwm: lcd0-bklt-pwm-state {
>> +		pins = "gpio59";
>> +		function = "gpio";
>> +		bias-disable;
>> +	};
>> +};
>> -- 
>> 2.34.1
>>