Re: [PATCH v2 0/7] ASoC: Intel: avs: Soundwire support

[Cezary Rojewski <cezary.rojewski@intel.com>]

On 11/4/2026 2:33 PM, Vinod Koul wrote:
> On 04-11-26, 12:52, Pierre-Louis Bossart wrote:
>> On 11/4/26 10:14, Cezary Rojewski wrote:
>>> On 11/3/2026 6:20 PM, Pierre-Louis Bossart wrote:
>>>>
>>>>> Also, the existing code fetches the PDIs based on pre-defined "dai_id".
>>>>> That's not the case for the avs-driver.  It simply asks: "is any PDI
>>>>> free?" and assigns it for the substream if one is found.
>>>>> No predefining.  Again, this aligns with how HDAudio streaming is done.
>>>> Yeah but at the end of the day there's a 1:1 mapping between cpu_dai and
>>>> PDI, no?
>>>>
>>>> All PDIs are created equal, a dynamic mapping doesn't make things more
>>>> efficient. It just makes things more complex to debug since you don't
>>>> have a fixed mapping between dailinks/stream/cpu_dai/PDI.
>>>>
>>>> Put differently, couldn't the AVS driver work around that fixed mapping
>>>> to avoid changes to legacy platforms that have shipped many moons ago?
>>>
>>> Kind disagree on the debugging part.  Having SDW streaming follow
>>> closely to what is done for HDAudio from the beginning (no hardcodes)
>>> makes it easier for a developer to debug stuff.  OTOH if one of these
>>> two follows a completely different path, the developer has to have such
>>> hardcodes in mind when debugging the PCM code or even when looking at
>>> the topology.
>>>
>>> At the same time, I'm not going anywhere and I do intend to work with
>>> Peter and Kai to update the common code. Simply put, such a refactor
>>> would be routed through SOF GH first.
>> The machine driver selects the first available cpu_dai when creating a
>> dailink. It doesn't really add much value to add a second level of
>> freedom to select PDIs, since in practice it'll select the first as
>> well. PDIs have no moral equivalent in HDaudio, it's a Cadence-specific  IP.
>>
>> Also there is already a degree of freedom in the allocation of
>> stream_tag, which is used for DMA support. That one makes sense since
>> DMAs may be used for non-SoundWire things (HDMI, trace, probe, etc).
>>
>> That's 2 degrees of freedom on 3 levels, do you really need full
>> configurability?

I'm not following this "level of freedom" notion. What's part of this
set is a basic allocation - driver (a user of the soundwire-lib) comes
and ask for a free resource (PDI). If there is one, it gets assigned.
Very standard, how many expect resources are redistributed.

> I dont see any gain from this approach. I would reconsider and see if we
> can reuse things
> 

I'm not sure which way the last message goes.

However, I find it easier to move from hardcodes to the basic allocation
approach (seen here, in this very patchset) than the other way around.
The change would consist of updating intel_hw_params() so the PDI
allocation is no longer done there.