[PATCH 4/4] ASoC: meson: aiu: use aiu-formatter-i2s to format I2S output data

[Jerome Brunet]

On jeu. 28 mai 2026 at 17:01, Valerio Setti <vsetti at baylibre.com> wrote:

> On 5/22/26 18:24, Valerio Setti wrote:
>> On 5/22/26 01:15, Mark Brown wrote:
>>> On Fri, May 15, 2026 at 05:10:40PM +0200, Valerio Setti wrote:
>>>> Create a new DAPM widget for "I2S formatter" and place it on the path
>>>> between FIFO and output DAI interface. Remove I2S output formatting code
>>>> from aiu-encoder-i2s since it's now implemented from aiu-formatter-i2s.
>>>
>>> This series, it looks like this specific patch, is breaking pcm-test on
>>> my libretech Le Potato board, the clocking looks to be seriously messed
>>> up.  I'm getting:
>>>
>>> [...]
>>>
>>> Full log:
>>>
>>>     https://lava.sirena.org.uk/scheduler/job/2786342#L1934
>>>
>>> The prior patches seem to test fine, it's this one that seems to
>>> introduce the issue.
>> Thanks a lot for the heads up and please apologize for the problem.
>> I wasn't aware of these testing tools so I based my testing on playing
>> with userspace alsa tools on the physical board that I have.
>> I will take a look at it ASAP and send a properly tested v2.
>> 
>
> Hi!
>
> I investigated a bit on the issue caused by my v1 patch series and I think
> I've found the root cause. I suspect my patch series helped discovering a
> misbehavior that was already present, so I'm seeking for suggestions on the
> proper way to proceed.
>
> # First: the background
>
> By default on OdroidC2/LePotato boards the only available audio playback is
> through HDMI. From DAI point of view the flow is as follows:
>
> "I2S FIFO" -> "I2S Encoder Playback" -> "CODEC CTRL HDMI I2S IN" -> "HDMI
> CTRL SRC" (mixer) -> "CODEC CTRL HDMI OUT Capture"
>
> In this chain the mixer "HDMI CTRL SRC" by default starts as "DISABLED" so
> it should prevent "CODEC CTRL HDMI OUT Capture" from receiving data.

Yes, leaving registers to their default state (even if it is not a
working configuration) and relying on mixer path to be setup was done on
purpose.

There is not a single configuration that would work/please everyone,
especially on AXG but the same could be said about the GX
series.

Not hardcoding any such configuration in the driver was the only sane
choice, even if it may seem to weird to have pipelines that do not work
by default.

>
> # What changed before/after the last commit of my patch series?
>
> - Before: "aiu-encoder-i2s.c" was calling "aiu_encoder_i2s_setup_desc()" in
>   "hw_params()". Audio playback shouldn't work in this condition because as
>   I mentioned "HDMI CTRL SRC"="DISABLED" by default, but apparently
>   configuring the AIU_I2S_SOURCE_DESC register is enough to make the
>  playback to work properly.

Nice :'(

>
> - After: those configurations are only set when "aiu_formatter_i2s_prepare"
>   is called which happens if "I2S Formatter" widget is enabled. Since "HDMI
>   CTRL SRC"="DISABLED" then "I2S Formatter" is not powered up and therefore
>   its callbacks are not called and the playback fails.
>
> Simply issuing the following command:
> $ amixer sset 'AIU HDMI CTRL SRC' 'I2S'
>
> resolves the problem and all pcm-tests pass.
> This also explains why I didn't catch this issue before sending the v1
> series: I tested with NXP SGTL5000 codec, not the HDMI one.
>
> # Final question
>
> I have 2 alternative proposals for this:
>
> - Change the default value of "HDMI CTRL SRC" so that at boot it's set to
>   some working configuration (ex: "I2S"). This should be done somewhere in
>  "aiu-codec-ctrl" I think.
> - Run the 'amixer' command above before running ALSA tests.
>
> Any suggestion on what's the best approach?

As Mark suggested, let be nice on the user and poke the register on
probe. Just add a big fat comment around it so it is clear why you are
doing it (and why it is not something to be copied)

>
> Thanks a lot.

-- 
Jerome