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

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Date:   Thu, 21 Jan 2021 15:41:23 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        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



On 21/01/2021 14:56, Pierre-Louis Bossart wrote:
> 
> 
>> 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?

[SLAVE]-------[MASTER]
NA-------------Port 1: PCM
Port 1---------Port 2: ADC 1 & 2
Port 2---------Port 3: ADC 3 & 4
Port 3---------Port 4: DMIC-0, DMIC-1, DIMC-2 , DMIC-3 and MBHC
Port 4---------Port 5: DMIC-4, DMIC-5, DMIC-6 and DMIC-7


Mapping is still static however Number of ports selection and channel 
mask will be dynamic here.


Example: for Headset MIC usecase we will be using Slv Port1, Slv Port3 
along with Mstr Port2 and Master Port4

Similarly for usecases like Digital MIC or other Analog MICs.


> 
>>> 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.

Is this on multi_link? which is why it might be working for you.

> 

Currently we have below check in sdw_stream_add_master().

if (!bus->multi_link && stream->m_rt_count > 0) {
	dev_err(bus->dev, "Multilink not supported, link %d\n", bus->link_id);
	ret = -EINVAL;
	goto unlock;
}

If we have single master(like my case) and dai-links which have more 
then one port  will be calling  sdw_stream_add_master() for each port, 
so m_rt_count above check will fail for the second call!



> 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. 

Master side.

> https://github.com/thesofproject/linux/pull/2514, we use DP2 and DP4 for 

This fine on slave side! Issue is on the master side!

> the same stream. This is done with the port_config capability.
> 
>