linux-kernel - Re: [PATCH 3/3] ASoC: fsl_asrc_dma: allocate memory from dma device

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Message-ID: <aXuUSnPSCa8YYfgd@lizhi-Precision-Tower-5810>
Date: Thu, 29 Jan 2026 12:09:30 -0500
From: Frank Li <Frank.li@....com>
To: Shengjiu Wang <shengjiu.wang@....com>
Cc: lgirdwood@...il.com, broonie@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, shawnguo@...nel.org,
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
	linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, shengjiu.wang@...il.com,
	Xiubo.Lee@...il.com, nicoleotsuka@...il.com, perex@...ex.cz,
	tiwai@...e.com, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 3/3] ASoC: fsl_asrc_dma: allocate memory from dma device

On Wed, Jan 28, 2026 at 03:18:53PM +0800, Shengjiu Wang wrote:
> As the dma device may support dma-coherent property on the i.MX952,
> allocate memory from dma device to make asrc driver to be compatible with
> such a case.
>
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> ---
>  sound/soc/fsl/fsl_asrc_dma.c | 48 ++++++++++++++++++++++++++++++------
>  1 file changed, 41 insertions(+), 7 deletions(-)
>
> diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
> index 7dacc06b2f02..b8fe242d53db 100644
> --- a/sound/soc/fsl/fsl_asrc_dma.c
> +++ b/sound/soc/fsl/fsl_asrc_dma.c
> @@ -449,18 +449,52 @@ fsl_asrc_dma_pcm_pointer(struct snd_soc_component *component,
>  static int fsl_asrc_dma_pcm_new(struct snd_soc_component *component,
>  				struct snd_soc_pcm_runtime *rtd)
>  {
> -	struct snd_card *card = rtd->card->snd_card;
> +	struct device *dev = component->dev;
> +	struct fsl_asrc *asrc = dev_get_drvdata(dev);
> +	struct fsl_asrc_pair *pair;
>  	struct snd_pcm *pcm = rtd->pcm;
> +	struct dma_chan *chan;
>  	int ret;
>
> -	ret = dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(32));
> -	if (ret) {
> -		dev_err(card->dev, "failed to set DMA mask\n");
> -		return ret;
> +	pair = kzalloc(sizeof(*pair) + asrc->pair_priv_size, GFP_KERNEL);

prefer use size_add(sizeof(*pair), asrc->pair_priv_size), which did
overflow check.

> +	if (!pair)
> +		return -ENOMEM;
> +
> +	pair->asrc = asrc;
> +	pair->private = (void *)pair + sizeof(struct fsl_asrc_pair);
> +
> +	/* Request a dummy pair, which will be released later.
> +	 * Request pair function needs channel num as input, for this
> +	 * dummy pair, we just request "1" channel temporarily.
> +	 */
> +	ret = asrc->request_pair(1, pair);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to request asrc pair\n");
> +		goto req_pair_err;
>  	}
>
> -	return snd_pcm_set_fixed_buffer_all(pcm, SNDRV_DMA_TYPE_DEV,
> -					    card->dev, FSL_ASRC_DMABUF_SIZE);
> +	/* Request a dummy dma channel, which will be released later. */
> +	chan = asrc->get_dma_channel(pair, IN);

Is it possible get real dma chan from fsl_asrc?

> +	if (!chan) {
> +		dev_err(dev, "failed to get dma channel\n");
> +		ret = -EINVAL;
> +		goto dma_chan_err;
> +	}
> +
> +	ret = snd_pcm_set_fixed_buffer_all(pcm,
> +					   SNDRV_DMA_TYPE_DEV,
> +					   chan->device->dev,
> +					   FSL_ASRC_DMABUF_SIZE);

Here you assume chan->device->dev never change when it did DMA transfer.

Frank
> +
> +	dma_release_channel(chan);
> +
> +dma_chan_err:
> +	asrc->release_pair(pair);
> +
> +req_pair_err:
> +	kfree(pair);
> +
> +	return ret;
>  }
>
>  struct snd_soc_component_driver fsl_asrc_component = {
> --
> 2.34.1
>