linux-kernel - Re: [PATCH v2 0/4] ASoC: qcom: display port changes

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Date: Tue, 23 Apr 2024 13:38:18 +0100
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: broonie@...nel.org, perex@...ex.cz, tiwai@...e.com, lgirdwood@...il.com,
 alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
 Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH v2 0/4] ASoC: qcom: display port changes

On 23/04/2024 12:59, Johan Hovold wrote:
> On Mon, Apr 22, 2024 at 02:43:50PM +0100, Srinivas Kandagatla wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>>
>> This patchset adds support for.
>> 	1. parse Display Port module tokens from ASoC topology
>> 	2. add support to DP/HDMI Jack events.
>> 	3. fixes a typo in function name in sm8250
>>
>> Verified these patches on X13s along with changes to tplg in
>> https://git.codelinaro.org/linaro/qcomlt/audioreach-topology/-/tree/topic/x13s-dp?ref_type=heads
>> and ucm changes from https://github.com/Srinivas-Kandagatla/alsa-ucm-conf/tree/topic/x13s-dp
> 
> It looks like your UCM changes are still muxing the speaker and *each*
> displayport output so that you can only use one device at a time (i.e.
> only Speaker or DP1 or DP2 can be used).
that is true.

What is the use-case to use more than one audio sink devices at the same 
time for a laptops?

How do you test it? I never tested anything like that on a full desktop 
setup.

May be some manual setup in Wireplumber, but not 100% sure about 
multiple stream handling.

> 
> As we discussed off list last week, this seems unnecessarily limited and
> as far as I understood is mostly needed to work around some
> implementation details (not sure why DP1 and DP2 can't be used in
> parallel either).

It is absolutely possible to run all the streams in parallel from the 
Audio hardware and DSP point of view.

One thing to note is, On Qualcomm DP IP, we can not read/write registers 
if the DP port is not connected, which means that we can not send data 
in such cases.

This makes it challenging to work with sound-servers like pipewire or 
pulseaudio as they tend to send silence data at very early stages in the 
full system boot up, ignoring state of the Jack events.

> 
> Can you please describe the problem here so that we can discuss this
> before merging an unnecessarily restricted solution which may later be
> harder to change (e.g. as kernel, topology and ucm may again need to be
> updated in lock step).
> 
>  From what I could tell after a quick look, this series does not
> necessarily depend on muxing things this way, but please confirm that
> too.

These patches have nothing to do with how we model the muxing in UCM or 
in tplg.

so these can go as it is irrespective of how we want to model the DP 
sinks in the UCM or tplg.

--srini
> 
> Johan