Date:   Tue, 17 Oct 2023 16:32:48 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>, mathias.nyman@...el.com,
        gregkh@...uxfoundation.org, lgirdwood@...il.com,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, srinivas.kandagatla@...aro.org,
        bgoswami@...cinc.com, Thinh.Nguyen@...opsys.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v9 09/34] ASoC: qcom: qdsp6: Introduce USB AFE port to
 q6dsp



On 10/17/23 15:00, Wesley Cheng wrote:
> The QC ADSP is able to support USB playback endpoints, so that the main

playback only?

> 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.

implicit feedback means support for capture. This is confusing...

> +static int q6usb_hw_params(struct snd_pcm_substream *substream,
> +			   struct snd_pcm_hw_params *params,
> +			   struct snd_soc_dai *dai)
> +{
> +	struct q6afe_dai_data *dai_data = dev_get_drvdata(dai->dev);
> +	int channels = params_channels(params);
> +	int rate = params_rate(params);
> +	struct q6afe_usb_cfg *usb = &dai_data->port_config[dai->id].usb_audio;
> +
> +	usb->sample_rate = rate;
> +	usb->num_channels = channels;
> +
> +	switch (params_format(params)) {
> +	case SNDRV_PCM_FORMAT_U16_LE:
> +	case SNDRV_PCM_FORMAT_S16_LE:
> +	case SNDRV_PCM_FORMAT_SPECIAL:

what does FORMAT_SPECIAL mean? the only other reference I see to this is
related to SLIMbus, not sure how this is related?

> +		usb->bit_width = 16;
> +		break;
> +	case SNDRV_PCM_FORMAT_S24_LE:
> +	case SNDRV_PCM_FORMAT_S24_3LE:
> +		usb->bit_width = 24;
> +		break;
> +	case SNDRV_PCM_FORMAT_S32_LE:
> +		usb->bit_width = 32;
> +		break;
> +	default:
> +		dev_err(dai->dev, "%s: invalid format %d\n",
> +			__func__, params_format(params));
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}

> @@ -617,6 +655,9 @@ static const struct snd_soc_dapm_route q6afe_dapm_routes[] = {
>  	{"TX_CODEC_DMA_TX_5", NULL, "TX_CODEC_DMA_TX_5 Capture"},
>  	{"RX_CODEC_DMA_RX_6 Playback", NULL, "RX_CODEC_DMA_RX_6"},
>  	{"RX_CODEC_DMA_RX_7 Playback", NULL, "RX_CODEC_DMA_RX_7"},
> +
> +	/* USB playback AFE port receives data for playback, hence use the RX port */
> +	{"USB Playback", NULL, "USB_RX"},

Capture for implicit feedback?

>  };
>  
>  static int msm_dai_q6_dai_probe(struct snd_soc_dai *dai)
> @@ -644,6 +685,18 @@ static int msm_dai_q6_dai_remove(struct snd_soc_dai *dai)
>  	return 0;
>  }
>  
> +static const struct snd_soc_dai_ops q6usb_ops = {
> +	.probe		= msm_dai_q6_dai_probe,
> +	.prepare	= q6afe_dai_prepare,
> +	.hw_params	= q6usb_hw_params,

this is rather confusing with two different layers used for hw_params
and prepare? Additional comments or explanations wouldn't hurt.

> +	.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.

This doesn't really explain why you need a shutdown?


> + * struct afe_param_id_usb_audio_dev_latency_mode
> + * @cfg_minor_version: Minor version used for tracking USB audio device
> + * configuration.
> + * Supported values:
> + *     AFE_API_MINOR_VERSION_USB_AUDIO_LATENCY_MODE
> + * @mode: latency mode for the USB audio device

what are the different latency modes? and is this related to the latency
reporting that was added in the USB2 audio class IIRC?

> +static int afe_port_send_usb_dev_param(struct q6afe_port *port, struct q6afe_usb_cfg *cfg)
> +{
> +	union afe_port_config *pcfg = &port->port_cfg;
> +	struct afe_param_id_usb_audio_dev_params usb_dev;
> +	struct afe_param_id_usb_audio_dev_lpcm_fmt lpcm_fmt;
> +	struct afe_param_id_usb_audio_svc_interval svc_int;
> +	int ret = 0;

useless init overridden...
> +
> +	if (!pcfg) {
> +		dev_err(port->afe->dev, "%s: Error, no configuration data\n", __func__);
> +		ret = -EINVAL;
> +		goto exit;
> +	}
> +
> +	memset(&usb_dev, 0, sizeof(usb_dev));
> +	memset(&lpcm_fmt, 0, sizeof(lpcm_fmt));
> +	memset(&svc_int, 0, sizeof(svc_int));
> +
> +	usb_dev.cfg_minor_version = AFE_API_MINOR_VERSION_USB_AUDIO_CONFIG;
> +	ret = q6afe_port_set_param_v2(port, &usb_dev,

.... here

> +				      AFE_PARAM_ID_USB_AUDIO_DEV_PARAMS,
> +				      AFE_MODULE_AUDIO_DEV_INTERFACE, sizeof(usb_dev));
> +	if (ret) {
> +		dev_err(port->afe->dev, "%s: AFE device param cmd failed %d\n",
> +			__func__, ret);
> +		goto exit;
> +	}
> +
> +	lpcm_fmt.cfg_minor_version = AFE_API_MINOR_VERSION_USB_AUDIO_CONFIG;
> +	lpcm_fmt.endian = pcfg->usb_cfg.endian;
> +	ret = q6afe_port_set_param_v2(port, &lpcm_fmt,
> +				      AFE_PARAM_ID_USB_AUDIO_DEV_LPCM_FMT,
> +				      AFE_MODULE_AUDIO_DEV_INTERFACE, sizeof(lpcm_fmt));
> +	if (ret) {
> +		dev_err(port->afe->dev, "%s: AFE device param cmd LPCM_FMT failed %d\n",
> +			__func__, ret);
> +		goto exit;
> +	}
> +
> +	svc_int.cfg_minor_version = AFE_API_MINOR_VERSION_USB_AUDIO_CONFIG;
> +	svc_int.svc_interval = pcfg->usb_cfg.service_interval;
> +	ret = q6afe_port_set_param_v2(port, &svc_int,
> +				      AFE_PARAM_ID_USB_AUDIO_SVC_INTERVAL,
> +				      AFE_MODULE_AUDIO_DEV_INTERFACE, sizeof(svc_int));
> +	if (ret)
> +		dev_err(port->afe->dev, "%s: AFE device param cmd svc_interval failed %d\n",
> +			__func__, ret);
> +
> +exit:
> +	return ret;
> +}

> -#define AFE_PORT_MAX		129
> +#define AFE_PORT_MAX		137

does this mean 8 ports are reserved for USB?

Or is this 137 just a random index coming from the AFE design?

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