Message-ID: <zlu5x6v2xkum67prrtk26r7govenczuntjvlrflvdb6lpd2ssy@jgrnl6elophe>
Date: Thu, 23 Oct 2025 15:24:41 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Srinivas Kandagatla <srinivas.kandagatla@....qualcomm.com>
Cc: Srinivas Kandagatla <srini@...nel.org>,
        Jianfeng Liu <liujianfeng1994@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        linux-arm-msm@...r.kernel.org, Xilin Wu <sophon@...xa.com>,
        David Airlie <airlied@...il.com>, Dmitry Baryshkov <lumag@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-sound@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v2] drm/display: add hw_params callback function to
 drm_connector_hdmi_audio_ops

On Thu, Oct 23, 2025 at 12:48:59PM +0100, Srinivas Kandagatla wrote:
> 
> 
> On 10/23/25 12:43 PM, Dmitry Baryshkov wrote:
> > On Sun, Oct 05, 2025 at 06:29:20PM +0300, Dmitry Baryshkov wrote:
> >> On Sat, Oct 04, 2025 at 02:16:08PM +0100, Srinivas Kandagatla wrote:
> >>>
> >>>
> >>> On 10/3/25 6:02 PM, Dmitry Baryshkov wrote:
> >>>> On Fri, Oct 03, 2025 at 05:35:16PM +0100, Srinivas Kandagatla wrote:
> >>>>>
> >>>>>
> >>>>> On 9/26/25 4:09 PM, Dmitry Baryshkov wrote:
> >>>>>> On Fri, Sep 26, 2025 at 11:30:26AM +0100, Srinivas Kandagatla wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> On 9/25/25 5:28 AM, Dmitry Baryshkov wrote:
> >>>>>>>> On Thu, Sep 25, 2025 at 12:05:09PM +0800, Jianfeng Liu wrote:
> >>>>>>>>> After reusing drm_hdmi_audio_* helpers and drm_bridge_connector
> >>>>>>>>> integration in drm/msm/dp, we have dropped msm_dp_audio_hw_params and
> >>>>>>>>> use msm_dp_audio_prepare instead. While userspace is still calling
> >>>>>>>>> hw_params to do audio initialization, and we get the following errors:
> >>>>>>>>>
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: q6apm_lpass_dai_prepare() started
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: q6apm_lpass_dai_prepare() started
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: q6apm_lpass_dai_prepare() started
> >>>>>>>>> hdmi-audio-codec hdmi-audio-codec.0.auto: hdmi_codec_hw_params() started
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: q6apm_lpass_dai_prepare() started
> >>>>>>>>> qcom-apm gprsvc:service:2:1: Error (1) Processing 0x01001002 cmd
> >>>>>>>>> qcom-apm gprsvc:service:2:1: DSP returned error[1001002] 1
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: Failed to start APM port 104
> >>>>>>>>> q6apm-lpass-dais 3700000.remoteproc:glink-edge:gpr:service@1:bedais: ASoC error (-22): at snd_soc_dai_prepare() on DISPLAY_PORT_RX_0
> >>>>>>>>> MultiMedia2 Playback: ASoC error (-22): at dpcm_run_update_startup() on MultiMedia2 Playback
> >>>>>>>>
> >>>>>>>> And a call to hdmi_codec_prepare() comes only at this place.
> >>>>>>>>
> >>>>>>>> Srini, Mark, when selecting to only implement .prepare for codec ops I
> >>>>>>>> was following the commit 2fef64eec23a ("ASoC: hdmi-codec: Add a prepare
> >>>>>>>> hook"), which documents that IEC958 status bit is set after
> >>>>>>>> .hw_params(), so it's only visible during .prepare(). Is it okay to
> >>>>>>>> implement both callbacks? Or should the audioreach DAI driver be fixed
> >>>>>>>> somehow instead (I suppose it assumes that the port is available after
> >>>>>>>> .hw_params(), not sure if that assumption is correct)?
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>> msm_dp_audio_prepare is not called because hdmi-codec driver only checks
> >>>>>>>>> and runs hw_params before q6apm_lpass_dai_prepare(). This commit will
> >>>>>>>>> add hw_params callback same as drm_connector_hdmi_audio_prepare, so that
> >>>>>>>>> hdmi-codec driver can work with userspace alsa.
> >>>>>>>>>
> >>>>>>>>> Tested with Radxa Dragon Q6A.
> >>>>>>>>>
> >>>>>>>>> Fixes: 98a8920e7b07 ("drm/msm/dp: reuse generic HDMI codec implementation")
> >>>>>>>>> Signed-off-by: Jianfeng Liu <liujianfeng1994@...il.com>
> >>>>>>>>
> >>>>>>>> The patch LGTM, but I would wait for response from audio maintainers.
> >>>>>>>>
> >>>>>>>
> >>>>>>> The ordering matters in this case as we need clocks and audio
> >>>>>>> configuration on DP codec side to be setup before we start configuring
> >>>>>>> the dsp pipeline. Looks like that DSP is trying to setup DP endpoint
> >>>>>>> even before it is ready.
> >>>>>>>
> >>>>>>> q6apm prepare loads the dsp pipeline and starts configuring the
> >>>>>>> endpoints, if the DP endpoint is not ready dsp would throw an error.
> >>>>>>>
> >>>>>>> We might be able to pull in some dsp logs to confirm this, but I dont
> >>>>>>> have a setup that I can reproduce this issue.
> >>>>>>
> >>>>>> What would be your recommendation to proceed? Is it okay for the DAI
> >>>>>> driver to depend on the .hw_params enabling the clock? Also I see that
> >>>>>> the error regarding the clocks comes from .prepare callback too. What is
> >>>>>> the order of .prepare callbacks()? Can we influence it?
> >>>>>
> >>>>> prepare follows hw-params, and prepare can be called multiple times
> >>>>>
> >>>>> When you mean order of prepare callbacks, you mean w.r.t codec and dsp
> >>>>> backend dia link drivers ?
> >>>>
> >>>> Yes. Here we got a dependency from the cpu dai to be prepare()'d after
> >>>> the DP driver performs some actions, which were a part of hw_params()
> >>>> callback but were moved to be executed during prepare() callback.
> >>>>
> >>>> This leads me to two sets of questions:
> >>>> - In which order are those callbacks executed? Can we make the ASoC
> >>>>   enforce some order of DAI's prepare() callbacks?
> >>>>
> >>>> - More improtantly, isn't it a sympthom of DP driver (incorrectly)
> >>>>   performing too much in the .hw_params() / .prepare() callback? Should
> >>>>   we move some of the setup to the .audio_startup() instead? What is the
> >>>>   expected split between those callbacks?
> >>>
> >>> I have not looked at full dp sequences but, if prepare is the only place
> >>> when it enables the required clocks for audio block, then it is a
> >>> problem, we should do it early so that DSP can enable the required
> >>> configuration in prepare.
> >>
> >> As I wrote, previously it was done as a part of hw_params, which is
> >> also not optimal as hdmi-codec clearly defines both callbacks as
> >> optional, requiring only one of them. Do you know, what is actually
> >> required on the DP side for the DSP to be able to preapre()?
> > 
> > Srinivas, did you have a chance to look at this? Or the .hw_prepare
> > ordering? I really don't want to land this fix only to face the same
> > issue because on some of the platforms .hw_prepare() callbacks will be
> > called in a different order.
> > 
> Dmitry, few days back Krzysztof was enabling DP audio on T14s, and we
> have seen that the DSP is not happy and returning error 1 when we try to
> prepare the dp port. The exact reason is codec is not ready at that point.
> 
> 
> By adding this patch, Krzystof managed to get DP working.
> XElite platforms were working before 2fef64eec23a ("ASoC: hdmi-codec:
> Add a prepare) patch was merged, basically 2fef64eec23a broke what was
> working before.
> 
> Am happy with this patch, better move to hw_params instead of prepare.

And I'm not happy with it :-)

hdmi-codec defines that one of the callbacks can be optional. We know
that at .hw_params time we don't have IEC 958 status bits, so we will be
programming incorrect audioframe.

Should some bits of code be moved to .audio_enable isntead? If so, which
bits?

I agree that there is a regression and that this patch fixes it. I argue
that the fix is incorrect.

-- 
With best wishes
Dmitry

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