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

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Message-ID: <ZlkEC-X2vzYEZ-Zl@eriador.lumag.spb.ru>
Date: Fri, 31 May 2024 01:56:11 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc: Johan Hovold <johan@...nel.org>, 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 Tue, Apr 23, 2024 at 01:38:18PM +0100, Srinivas Kandagatla wrote:
> 
> 
> 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?

Consider multi-seat setup, with each monitor having its own set of
keyboard, mouse, headphone and user behind it.

> 
> 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.

How is this handled for the native HDMI playback on platforms like
Dragonboard 820c? As far as I was able to test, playback fails with -EIO
if HDMI output is not enabled or if the DVI monitor is connected.

> 
> 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

-- 
With best wishes
Dmitry