linux-kernel - Re: [PATCH v26 19/33] ASoC: qcom: qdsp6: Introduce USB AFE port to q6dsp

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Message-ID: <ae0ae5f0-a3e9-49b4-95ba-524975d70659@linux.intel.com>
Date: Fri, 30 Aug 2024 11:12:50 +0200
From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To: Wesley Cheng <quic_wcheng@...cinc.com>, srinivas.kandagatla@...aro.org,
 mathias.nyman@...el.com, perex@...ex.cz, conor+dt@...nel.org,
 dmitry.torokhov@...il.com, corbet@....net, broonie@...nel.org,
 lgirdwood@...il.com, tiwai@...e.com, krzk+dt@...nel.org,
 Thinh.Nguyen@...opsys.com, bgoswami@...cinc.com, robh@...nel.org,
 gregkh@...uxfoundation.org
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-input@...r.kernel.org,
 linux-usb@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-doc@...r.kernel.org, alsa-devel@...a-project.org
Subject: Re: [PATCH v26 19/33] ASoC: qcom: qdsp6: Introduce USB AFE port to
 q6dsp



On 8/29/24 21:40, Wesley Cheng wrote:
> The QC ADSP is able to support USB playback endpoints, so that the main
> application processor can be placed into lower CPU power modes.  This adds
> the required AFE port configurations and port start command to start an
> audio session.
> 
> Specifically, the QC ADSP can support all potential endpoints that are
> exposed by the audio data interface.  This includes, feedback endpoints
> (both implicit and explicit) as well as the isochronous (data) endpoints.

I think you meant

"
this includes isochronous data endpoints, in either synchronous mode or
asynchronous mode. In the latter case both implicit or explicit feedback
endpoints are supported.
"

And now I don't remember how *controls* are handled.

Is this the case that all controls exposed by endpoint zero are visible
in both the regular USB-audio card AND the offloaded card, with changes
mirrored?

It's important to explain so that the volumes are consistent no matter
which path is used. This should be added to the documentation.


> +static const struct snd_soc_dai_ops q6afe_usb_ops = {
> +	.probe		= msm_dai_q6_dai_probe,
> +	.prepare	= q6afe_dai_prepare,
> +	.hw_params	= q6afe_usb_hw_params,
> +	/*
> +	 * Shutdown callback required to stop the USB AFE port, which is enabled
> +	 * by the prepare() stage.  This stops the audio traffic on the USB AFE
> +	 * port on the Q6DSP.
> +	 */
> +	.shutdown	= q6afe_dai_shutdown,
> +	/*
> +	 * Startup callback not needed, as AFE port start command passes the PCM
> +	 * parameters within the AFE command, which is provided by the PCM core
> +	 * during the prepare() stage.
> +	 */

Humm, now this is a bit confusing. Why would you need a shutdown, can't
you use the hw_free() callback for symmetry with prepare()?