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

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Date: Tue, 23 Apr 2024 16:59:56 +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 15:58, Johan Hovold wrote:
>> 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.
> This bit sounds like it can and should be worked around by the driver to
> avoid hard-coding policy which would prevent use cases such as the ones
> mentioned above.
This is not simple as you say. We have to fit these into a proper DPCM.
Either we have a dummy Backend connected for each of these pcm 
sub-devices when DP port is not connected and then switch back to DP 
when its connected.

Or somehow find a way to not let the pipewire talk to devices which are 
not connected.


thanks,
srini