Message-ID: <bnrpfijh4rljdzroduqncfygysvgblljlhdpvq7ubajlbbwvwd@ohdmpjvpzj33>
Date: Fri, 3 Oct 2025 20:02:37 +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>,
        Abhinav Kumar <quic_abhinavk@...cinc.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
Subject: Re: [PATCH v2] drm/display: add hw_params callback function to
 drm_connector_hdmi_audio_ops

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?

> 
> TBH, Am not sure, I did not find anything that was obvious from the code.
> 
> 
> 
> --srini
> 
> 
> 
> > 
> >>
> >>
> >> --srini
> >>>> ---
> >>>>
> >>>> Changes in v2:
> >>>> - Link to v1: https://lore.kernel.org/linux-arm-msm/20250924085804.34183-1-liujianfeng1994@gmail.com/
> >>>> - Use more detailed trace log in commit message.
> >>>> - Drop the empty line between Fixex and SoB.
> >>>>
> >>>>  drivers/gpu/drm/display/drm_hdmi_audio_helper.c | 1 +
> >>>>  1 file changed, 1 insertion(+)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/display/drm_hdmi_audio_helper.c b/drivers/gpu/drm/display/drm_hdmi_audio_helper.c
> >>>> index 7d78b02c1446..6ca1c7ad0632 100644
> >>>> --- a/drivers/gpu/drm/display/drm_hdmi_audio_helper.c
> >>>> +++ b/drivers/gpu/drm/display/drm_hdmi_audio_helper.c
> >>>> @@ -130,6 +130,7 @@ EXPORT_SYMBOL(drm_connector_hdmi_audio_plugged_notify);
> >>>>  
> >>>>  static const struct hdmi_codec_ops drm_connector_hdmi_audio_ops = {
> >>>>  	.audio_startup = drm_connector_hdmi_audio_startup,
> >>>> +	.hw_params = drm_connector_hdmi_audio_prepare,
> >>>>  	.prepare = drm_connector_hdmi_audio_prepare,
> >>>>  	.audio_shutdown = drm_connector_hdmi_audio_shutdown,
> >>>>  	.mute_stream = drm_connector_hdmi_audio_mute_stream,
> >>>> -- 
> >>>> 2.43.0
> >>>>
> >>>
> >>
> > 
> 

-- 
With best wishes
Dmitry

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