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

From: Vinod Koul <vkoul@kernel.org>
To: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	yung-chuan.liao@linux.intel.com, gregkh@linuxfoundation.org,
	sanyog.r.kale@intel.com, alsa-devel@alsa-project.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] soundwire: add support for static port mapping
Date: Mon, 1 Feb 2021 15:57:09 +0530	[thread overview]
Message-ID: <20210201102709.GT2771@vkoul-mobl> (raw)
In-Reply-To: <31ff9d2b-760a-374e-5b37-45d8e8116f7b@linaro.org>

On 25-01-21, 16:23, Srinivas Kandagatla wrote:
> 
> 
> On 22/01/2021 16:42, Pierre-Louis Bossart wrote:
> > > > 
> > > > if you completely remove the stream and re-add it with updated
> > > > configuration things should work.
> > > 
> > > That's exactly what we do currently!
> > > 
> > > The updated ports due to new configuration ex: for "mic capture"
> > > dailink needs to be communicated from slave(codec) to master so that
> > > it can allocate correct ports. That is what this patch is trying to
> > > do (share current port map information).
> > 
> > .. we have a disconnect on how to do this configuration update.
> > 
> > The 'stream' support was designed so that a stream can be split across
> > multiple devices (both masters and slaves). With this design we need to
> > have a central configuration and distribute the information to all
> > devices taking part of the stream.

That is correct, but in this case a stream consists of one master and
one or more slave devices. This is not a multi-master design. The adding
of multiple masters should not be done here... that does not seem
logically right in this situation

> > It seems you are in a different solution-space, where the codec driver
> > needs to notify the master of which ports it needs to use?
> 
> Correct! As Codec is the place where we have mixer controls ant it can
> clearly tell which master ports should be used for that particular
> configuration.

And that should come from firmware (DT etc) and driver should pass on
this info

> > I also don't see where the mapping is actually set. Patch 2 uses a
> > mapping but there's no codec driver change that defines the mapping?
> > 
> > Do you actually call sdw_stream_add_slave() with a new mapping?
> > 
> Yes, currently am working on a codec driver for WCD938x Codec, which I will
> posting very soon!
> 
> > It feels we are missing the codec part to really see what you are trying
> > to do?
> My WIP code is at https://git.linaro.org/people/srinivas.kandagatla/linux.git/tree/sound/soc/codecs/wcd938x.c?h=wcd938x/wip#n4526
> 
> Currently the master ports are hardcoded in the driver for now, but these
> will come from DT.
> 
> --srini

-- 
~Vinod