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

From: Pierre-Louis Bossart
Date: Fri Jan 22 2021 - 10:36:07 EST

On 1/22/21 1:05 AM, Srinivas Kandagatla wrote:

On 21/01/2021 21:30, Pierre-Louis Bossart wrote:

Am looking at intel_hw_params(). Isn't sdw_stream_add_master() called for every dai in the dai link.

Yes, that's correct, but again a dai may use one or more ports.

if you defined each port as a dai, and want to call sdw_stream_add_master() for each port you are doing something the API was not designed for. There is a 'num_ports' argument for a reason :-)

per master, and that master_rt deals with one or more ports - your choice. >
A 'stream' is an abstract data transport which can be split across multiple masters/sales and for each master/slave use multiple ports.
When calling sdw_stream_add_master/slave, you need to provide a port_config/num_ports to state which ports will be used on that master/slave when using the stream. That's how we e.g. deal with 4ch streams that are handled by two ports on each side.

To up-level a bit, the notion of 'stream' is actually very very similar to the notion of dailink. And in fact, the 'stream' is actually created for Intel in the dailink .startup callback, so I am quite in the dark on what you are trying to accomplish.
In qcom case stream is also allocated for in dai startup().

I think we are talking about two different issues,

1>one is the failure I see in sdw_stream_add_master() when I try to use dai-link dai-id style approach suggested. I will dig this bit more and collect more details!

2>(Main issue) Ability for slave to select different combination of ports at runtime based on the mixer setting or active dapm.

All this patch is trying do is the pass this *CURRENT/ACTIVE* static port mapping between slave and master while setting up the stream.
With the dailink approach number of ports are pretty much static and may not be required for particular use case. As above example if we have a headset with button click suppression we would need 2 Ports and similarly without we only need one port.

As I said above you cannot enable the button click suppression dynamically *after* the headset capture hw_params/prepare.

That is not true, the ports in this case are selected based on mixer setting or register state even before stream is setup/started in hw_params/prepare.
WSA881x codec has pretty much similar setup.

we are saying the same thing, the configuration provided is only taken into account when setting-up the stream in hw_params. mixer or configuration changes after that step are ignored.

If you follow what we've done at Intel with the sdw_stream_add_master() called in the .hw_params phase, and conversely call sdw_stream_remove_master() in .hw_free, you should be good to go.

You will note that we have a notification to the DSP, so you can manage resources in your firmware, there is no need to oversubscribe but only allocate what is required for a given use case.

This is not possible with dai-link approach, unless we create two different dai links for the above example usecase!

The current approach is a worst-case one, where you would create a single 'headset capture' dailink.

Are you suggesting that we have dailink for each usecase like:

"headset capture"
"Analog MIC1 capture"
"Analog MIC2 Capture"


"Analog MIC4 Capture"


"DMIC0 capture"
"DMIC1 Capture"
"DMIC2 Capture"


"DMIC7 Capture"
"Headset Playback"
"Ear Playback"
"Aux Playback"

this is not really doable!

No, what I was saying is that you need to define multiple streams e.g.
- headset capture (configured with or without click suppression)
- mic capture (configured with AMICs or DMICs)
- playback (or possibly different endpoint specific streams depending on whether concurrency between endpoint is possible)

if you change the configuration, you have to tear down the stream and reconfigure it - and for this we already have the required API and you can guarantee that the configuration for that stream is consistent between master and slave(s).

All am saying is that codec can decide which ports it has to select based on mixer setting before the stream is setup/started. This updated mapping between slv port and master ports is passed as part of the port_config in sdw_stream_add_slave().

if you completely remove the stream and re-add it with updated configuration things should work.