linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: x1e78100-t14s: Add audio playback over DisplayPort

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Message-ID: <82971ca7-8f52-4350-947f-309e913a6886@oss.qualcomm.com>
Date: Mon, 27 Oct 2025 13:43:05 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov
 <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: dts: qcom: x1e78100-t14s: Add audio playback
 over DisplayPort

On 10/27/25 1:38 PM, Krzysztof Kozlowski wrote:
> On 27/10/2025 13:20, Konrad Dybcio wrote:
>> On 10/21/25 1:10 PM, Krzysztof Kozlowski wrote:
>>> Add necessary DAI links and DAI name prefixes to enable audio playback
>>> over USB/DisplayPort and HDMI.  The HDMI port is not yet enabled, but it
>>> should carry respective DAI name prefix regardless.
>>>
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>
>>> ---
>>>
>>> ALSA UCM and audioreach topology will follow up as well.
>>> ---
>>
>> [...]
>>
>>>  &mdss_dp0 {
>>> +	sound-name-prefix = "DisplayPort0";
>>
>> We should probably push this into SoC dtsi since #sound-dai-cells
>> is there
> 
> 
> Hm, that's important for user-space and represents actual naming or
> wiring on the board, so it is strictly a board property. IOW, there
> could be a board which does not have DP0, thus mdss_dp1 should be called
> DP0.
> 
> If you are sure that such case does not exist, then indeed we can make
> it shared.

On at least x1e, any of DP012 (not 3) host can be re-routed to any
QMPPHY output, at runtime, so I'd rather keep this bound to the DP host
index.

This is utilized e.g. for USB4 or MST. Or if someone has a fantasy for
remapping their PHY<->DP links for no good reason.

Konrad