Re: [PATCH v1 0/4] Add static channel mapping between soundwire master and slave

[Pierre-Louis Bossart]

On 9/9/24 12:55, Mohammad Rafi Shaik wrote:
> Add static channel map support between soundwire master and slave.
> This patch series will resolve channel mask mismatch between master and slave.
> 
> Scenario: wcd937x AMIC2 usecase
> 
>                           Master                 Slave (wcd937x)
>                      +--------------+           +--------------+
>                      |  +--------+  |           |  +--------+  |
>          AMIC1 ----->|  | PORT1  |  |           |  |   TX1  |  |<-----------AMIC1
>          AMIC2 ----->|  |        |  |           |  |        |  |
>                      |  +--------+  |           |  +--------+  |
>                      |              |           |              |
>          AMIC3 ----->|  +--------+  |           |  +--------+  |
>                      |  |  PORT2 |  |           |  |   TX2  |  |<-----------AMIC2
>                      |  |        |  |           |  |        |  |<-----------AMIC3
>                      |  +--------+  |           |  +--------+  |
>                      |              |           |              |
>                      |  +--------+  |           |  +--------+  |
>  DMIC0...DMIC3------>|  |  PORT3 |  |           |  |   TX3  |  |<-----------DMIC0...DMIC3
>                      |  |        |  |           |  |        |  |<-----------MBHC
>                      |  +--------+  |           |  +--------+  |
>                      |              |           |              |
>                      |  +--------+  |           |  +--------+  |
>  DMIC4...DMIC37----->|  |  PORT4 |  |           |  |   TX4  |  |<-----------DMIC4...DMIC7
>                      |  |        |  |           |  |        |  |
>                      |  +--------+  |           |  +--------+  |
>                      |              |           |              |
>                      +------------- +           +--------------+
> 
> For AMIC2 usecase, The Slave need to configure TX2 Port with channel mask 1 and
> for Master required PORT1 with channel mask 2,
> 
> In existing design master and slave configured with same channel mask, it will fail
> AMIC2 usecase.
> 
> The New design will help to configure channel mapping between master and slave from
> device tree.

That's rather controversial...

In theory you already have the means to deal with a different channel
mapping in the hw_params callback for your manager and peripheral
devices. That's how we e.g. send a 2ch stream on the manager to two
separate amplifiers and program which channel is used by what amplifier.

The common part between manager and peripheral is the notion of
'stream', and you can add a different port/stream configuration for
manager and peripheral with sdw_stream_add_master() and
sdw_stream_add_slave() respectively.

Port1 and TX2 can be used by just setting the relevant port_config.num
value.

Likewise the port_config.ch_mask can be programmed at will to select the
relevant mappings. See e.g. rt1308_sdw_hw_params() in rt1308-sdw.c, the
mapping were handled with a set_tdm_slot() callback before.

In short, please re-visit your hw_params() implementation first and use
the existing 'stream' APIs.