Re: [PATCH v2] drm/display: add hw_params callback function to drm_connector_hdmi_audio_ops

[Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>]

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@gmail.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 ?

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
>>>>
>>>
>>
>