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

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Message-ID: <CAA+D8AM2d8m2eZnenH7gqOEUO1dLifFSNgizRRXwOiLX2vVdTA@mail.gmail.com>
Date: Fri, 30 Jan 2026 09:52:26 +0800
From: Shengjiu Wang <shengjiu.wang@...il.com>
To: Frank Li <Frank.li@....com>
Cc: Shengjiu Wang <shengjiu.wang@....com>, 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, 
	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 Fri, Jan 30, 2026 at 1:09 AM Frank Li <Frank.li@....com> wrote:
>
> 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.

Ok, will update it.

>
> > +     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?

This is real dma chan, may be I should remove "dummy".

>
> > +     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.

Yes, this refers to the generic code in ALSA.

best regards
Shengjiu Wang

>
> 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
> >