linux-kernel - Re: [PATCH v1] arm64: dts: qcom: talos-evk: Add ADV7535 DSI-to-HDMI bridge

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Message-ID: <b3390184-a3ef-49f6-8b68-dbf94564ab43@gmail.com>
Date: Thu, 16 Oct 2025 14:24:40 +0530
From: Tessolve Upstream <tessolveupstream@...il.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: andersson@...nel.org, konradybcio@...nel.org, 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 v1] arm64: dts: qcom: talos-evk: Add ADV7535 DSI-to-HDMI
 bridge



On 15/10/25 18:34, Dmitry Baryshkov wrote:
> On Wed, Oct 15, 2025 at 05:58:08PM +0530, Sudarshan Shetty wrote:
>> Hook up the ADV7535 DSI-to-HDMI bridge on the QCS615 Talos EVK board.
>> This provides HDMI output through the external DSI-to-HDMI converter.
>>
>> Signed-off-by: Sudarshan Shetty <tessolveupstream@...il.com>
>> ---
>>  arch/arm64/boot/dts/qcom/talos-evk-som.dtsi | 21 ++++++
>>  arch/arm64/boot/dts/qcom/talos-evk.dts      | 76 +++++++++++++++++++++
>>  2 files changed, 97 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/talos-evk-som.dtsi b/arch/arm64/boot/dts/qcom/talos-evk-som.dtsi
>> index 55ec8034103d..b58cae02c9cb 100644
>> --- a/arch/arm64/boot/dts/qcom/talos-evk-som.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/talos-evk-som.dtsi
>> @@ -244,6 +244,27 @@ eeprom@5f {
>>  	};
>>  };
>>  
>> +&mdss {
>> +	status = "okay";
>> +};
>> +
>> +&mdss_dsi0 {
>> +	vdda-supply = <&vreg_l11a>;
>> +
>> +	status = "okay";
>> +};
>> +
>> +&mdss_dsi0_out {
>> +	remote-endpoint = <&adv7535_in>;
>> +	data-lanes = <0 1 2 3>;
>> +};
>> +
>> +&mdss_dsi0_phy {
>> +	vdds-supply = <&vreg_l5a>;
>> +
>> +	status = "okay";
>> +};
>> +
>>  &pcie {
>>  	perst-gpios = <&tlmm 101 GPIO_ACTIVE_LOW>;
>>  	wake-gpios = <&tlmm 100 GPIO_ACTIVE_HIGH>;
>> diff --git a/arch/arm64/boot/dts/qcom/talos-evk.dts b/arch/arm64/boot/dts/qcom/talos-evk.dts
>> index 25057f4f6a91..f7e8be3667d1 100644
>> --- a/arch/arm64/boot/dts/qcom/talos-evk.dts
>> +++ b/arch/arm64/boot/dts/qcom/talos-evk.dts
>> @@ -14,6 +14,82 @@ / {
>>  	aliases {
>>  		mmc1 = &sdhc_2;
>>  	};
>> +
>> +	hdmi-out {
>> +		compatible = "hdmi-connector";
>> +		type = "d";
>> +
>> +		port {
>> +			hdmi_con_out: endpoint {
>> +				remote-endpoint = <&adv7535_out>;
>> +			};
>> +		};
>> +	};
>> +
>> +	vreg_v1p2_out: regulator-v1p2-out {
>> +		compatible = "regulator-fixed";
>> +		regulator-name = "vreg-v1p2-out";
>> +		regulator-min-microvolt = <1200000>;
>> +		regulator-max-microvolt = <1200000>;
>> +		regulator-boot-on;
>> +		regulator-always-on;
>> +	};
>> +
>> +	vreg_v1p8_out: regulator-v1p8-out {
>> +		compatible = "regulator-fixed";
>> +		regulator-name = "vreg-v1p8-out";
>> +		regulator-min-microvolt = <1800000>;
>> +		regulator-max-microvolt = <1800000>;
>> +		regulator-boot-on;
>> +		regulator-always-on;
>> +	};
>> +
>> +	vreg_v3p3_out: regulator-v3p3-out {
>> +		compatible = "regulator-fixed";
>> +		regulator-name = "vreg-v3p3-out";
>> +		regulator-min-microvolt = <3300000>;
>> +		regulator-max-microvolt = <3300000>;
>> +		regulator-boot-on;
>> +		regulator-always-on;
>> +	};
> 
> Please describe the power grid. Are these regulators being fed by
> nothing and generating energy from the thin air?

Thanks for the feedback.
You are right — in the previous patch, the regulators appeared
to have no source, which was incorrect.

To clarify the hardware design:
The 3.3 V and 1.8 V supplies to the HDMI controller are not coming 
from the PMIC. They are generated on the carrier board as follows:

20 V (USBC_VBUS_IN) → 5 V rail (V5P0_OUT)
→ 3.3 V buck regulator (RAA211250) and 1.8 V LDO (TPS7A9101).

The 5 V rail (V5P0_OUT) acts as the input supply for both regulators.
Both regulators are always on.

example:
v5p0_out: regulator-v5p0-out {
    compatible = "regulator-fixed";
    regulator-name = "v5p0_out";
    regulator-min-microvolt = <5000000>;
    regulator-max-microvolt = <5000000>;
    regulator-always-on;
    regulator-boot-on;
};

v3p3_out: regulator-v3p3-out {
    compatible = "regulator-fixed";
    regulator-name = "v3p3_out";
    regulator-min-microvolt = <3300000>;
    regulator-max-microvolt = <3300000>;
    vin-supply = <&v5p0_out>;
    regulator-always-on;
    regulator-boot-on;
};

v1p8_out: regulator-v1p8-out {
    compatible = "regulator-fixed";
    regulator-name = "v1p8_out";
    regulator-min-microvolt = <1800000>;
    regulator-max-microvolt = <1800000>;
    vin-supply = <&v5p0_out>;
    regulator-always-on;
    regulator-boot-on;
};

These reflect the actual power grid of the board.
The 20 V input is not modeled since it’s a raw external
supply and not managed by Linux.

Please let me know if this structure looks acceptable,
Thanks again for the review and guidance!
> 
>> +};
>> +
>> +&i2c1 {
>> +	clock-frequency = <400000>;
>> +
>> +	status = "okay";
>> +
>> +	adv7535: adv7535@3d {
>> +		compatible = "adi,adv7535";
>> +		reg = <0x3d>;
>> +		avdd-supply = <&vreg_v1p8_out>;
>> +		dvdd-supply = <&vreg_v1p8_out>;
>> +		pvdd-supply = <&vreg_v1p8_out>;
>> +		a2vdd-supply = <&vreg_v1p8_out>;
>> +		v3p3-supply = <&vreg_v3p3_out>;
>> +		v1p2-supply = <&vreg_v1p2_out>;
> 
> I think this is not correct. Please consult your schematics isntead of
> adding dummy regulators.

Will take care in v2 patch.
> 
>