linux-kernel - Re: meson-aiu: HDMI codec .prepare() callback not called

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Message-ID: <CAFBinCA2pz+ZeWr2hA-QRwZ5gC70qp=2iqemX5MpyM75cAbJwg@mail.gmail.com>
Date: Mon, 6 Jan 2025 14:38:28 +0100
From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: linux-amlogic@...ts.infradead.org, linux-sound@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	dmitry.baryshkov@...aro.org
Subject: Re: meson-aiu: HDMI codec .prepare() callback not called

Hi Jerome,

On Mon, Jan 6, 2025 at 2:24 PM Jerome Brunet <jbrunet@...libre.com> wrote:
>
> On Mon 06 Jan 2025 at 13:49, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:
>
> > Hi Jerome,
> >
> > On Mon, Jan 6, 2025 at 11:44 AM Jerome Brunet <jbrunet@...libre.com> wrote:
> > [...]
> >> > I have further verified that the gx-card parsing does find the HDMi
> >> > controller and links it correctly.
> >> > To me it's odd that only the .prepare() callback is not called, all
> >> > others (as mentioned above: .hw_params, .startup, ...) are working
> >> > fine.
> >>
> >> I think the problem you are seeing comes from the quirk of
> >> codec-to-codec links. The hdmi codec link is such a link on Amlogic
> >> because further digital routing is required after the backend.
> >>
> >> Those type of links are not used much beside some
> >> CPU offloading on Samsung and Amlogic, as far as I know.
> >> It is possible, even likely, that things are still missing there.
> >>
> >> So those C2C links are operated by the DAPM events, not the regualar
> >> ASoC code. You can start here:
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/soc/soc-dapm.c#n3995
> > Thank you - that is indeed the root cause!
> >
> >> You'll see that .prepare() is not called, same as .trigger()
> >> That should propably be fixed :/
> > Since I'm still very much clueless about all of this I just came up
> > with an experimental patch. Any feedback on it is welcome (I can send
> > it as RFC patch - but prepare for me needing support).
>
> It is probably a good idea to send it to get more feedback, yes.
Sure, I'll do that later and keep you Cc'ed.

> > With the attached patch I now see hdmi-codec's .prepare callback being called:
>
> Looks like a good start :)
>
> Couples of nitpicks:
>
> You might want to check the stream validity in
> the function you've introduced, like in soc_dai_trigger()
snd_soc_dai_hw_params() doesn't check it either but snd_soc_dai_startup() does.

> It may also be nice to update snd_soc_pcm_dai_prepare() with the
> introduced function.
Ah, this one is also checking for substream validity. That explains
your previous suggestion :-)


Best regards,
Martin