linux-kernel - Re: [RFC PATCH 1/2] soundwire: add support for static port mapping

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Date:   Thu, 21 Jan 2021 08:56:23 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        vkoul@...nel.org, yung-chuan.liao@...ux.intel.com
Cc:     gregkh@...uxfoundation.org, sanyog.r.kale@...el.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] soundwire: add support for static port mapping



> Port allocations are something like this:
> 
> RX: (Simple)
> Port 1 -> HPH L/R
> Port 2 -> CLASS H Amp
> Port 3 -> COMP
> Port 4 -> DSD.
> 
> TX: (This get bit more complicated)
> Port 1: PCM
> Port 2: ADC 1 & 2
> Port 3: ADC 3 & 4
> Port 4: DMIC-0, DMIC-1, DIMC-2 , DMIC-3 and MBHC
> Port 5: DMIC-4, DMIC-5, DMIC-6 and DMIC-7
> 
> We handle the port allocation dynamically based on mixer and dapm 
> widgets in my code! Also channel allocations are different for each 
> function!

Sorry, I am not following here. What is dynamic here and use-case 
dependent? And is this a mapping on the master or the codec sides that 
you want to modify?

>> Does this help and can you align on what Intel started with?
> 
> Firstly, This is where the issue comes, if we go with the 
> suggested(dai->id) solution, we would end up with a long list of 
> dai-links with different combinations of both inputs/output connections 
> and usecases. Again we have to deal with limited DSP resources too!
> 
> Secondly, The check [1] in stream.c will not allow more than one master 
> port config to be added to master runtime. Ex: RX Port 1, 2, 3 is used 
> for Headset Playback.

I am confused here, we do have examples in existing codec drivers where 
we use multiple ports for a single stream, e.g. for IV feedback we use 2 
ports.

In your "RX Port 1, 2, 3" example, are you referring to the codec or the 
master side? If it's for the codec, it's already supported, see e.g. 
https://github.com/thesofproject/linux/pull/2514, we use DP2 and DP4 for 
the same stream. This is done with the port_config capability.