linux-kernel - Re: [PATCH 2/3] ASoC: fsl_asrc: Add support for i.MX952 platform

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Message-ID: <CAA+D8AMYEVbFTgTaVhTU_ZJ=eoyQAj4zygLsfuK+Yt+=8qQk1Q@mail.gmail.com>
Date: Fri, 30 Jan 2026 09:44:45 +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 2/3] ASoC: fsl_asrc: Add support for i.MX952 platform

On Fri, Jan 30, 2026 at 1:14 AM Frank Li <Frank.li@....com> wrote:
>
> On Wed, Jan 28, 2026 at 03:18:52PM +0800, Shengjiu Wang wrote:
> > Add a compatible string and clock mapping table to support ASRC on the
> > i.MX952 platform.
> >
> > There is a limitation on i.MX952 that dma request is not cleared at the
> > end of conversion with dma slave mode. Which causes sample is dropped
> > from the input fifo on the second time if dma is triggered before the
> > client device and EDMA may copy wrong data from output fifo as the output
> > fifo is not ready in the beginning.
> >
> > So need to trigger asrc before dma on i.MX952, and add delay to wait
> > output data is generated then start the EDMA for output, otherwise the
> > m2m function has noise issues.
> >
> > Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> > ---
> >  sound/soc/fsl/fsl_asrc.c        | 39 +++++++++++++++++++++++++++++++++
> >  sound/soc/fsl/fsl_asrc.h        | 16 ++++++++++++++
> >  sound/soc/fsl/fsl_asrc_common.h |  3 +++
> >  sound/soc/fsl/fsl_asrc_m2m.c    | 29 +++++++++++++++++-------
> >  4 files changed, 79 insertions(+), 8 deletions(-)
> >
> ...
> > diff --git a/sound/soc/fsl/fsl_asrc_m2m.c b/sound/soc/fsl/fsl_asrc_m2m.c
> > index f46881f71e43..296e13a16490 100644
> > --- a/sound/soc/fsl/fsl_asrc_m2m.c
> > +++ b/sound/soc/fsl/fsl_asrc_m2m.c
> > @@ -253,15 +253,28 @@ static int asrc_m2m_device_run(struct fsl_asrc_pair *pair, struct snd_compr_task
> >       reinit_completion(&pair->complete[IN]);
> >       reinit_completion(&pair->complete[OUT]);
> >
> > -     /* Submit DMA request */
> > -     dmaengine_submit(pair->desc[IN]);
> > -     dma_async_issue_pending(pair->desc[IN]->chan);
> > -     if (out_dma_len > 0) {
> > -             dmaengine_submit(pair->desc[OUT]);
> > -             dma_async_issue_pending(pair->desc[OUT]->chan);
> > -     }
> > +     if (asrc->start_before_dma) {
> > +             asrc->m2m_start(pair);
>
> Does other Soc also work if ASRC start before DMA enable? Suppose most like
> work. Then needn't start_before_dma.

Yes, should work.  but I don't want to change the original behaviour
of other SoC.

Best regards
Shengjiu Wang
>
> Frank
>
> > +             /* Submit DMA request */
> > +             dmaengine_submit(pair->desc[IN]);
> > +             dma_async_issue_pending(pair->desc[IN]->chan);
> > +             if (out_dma_len > 0) {
> > +                     if (asrc->m2m_output_ready)
> > +                             asrc->m2m_output_ready(pair);
> > +                     dmaengine_submit(pair->desc[OUT]);
> > +                     dma_async_issue_pending(pair->desc[OUT]->chan);
> > +             }
> > +     } else {
> > +             /* Submit DMA request */
> > +             dmaengine_submit(pair->desc[IN]);
> > +             dma_async_issue_pending(pair->desc[IN]->chan);
> > +             if (out_dma_len > 0) {
> > +                     dmaengine_submit(pair->desc[OUT]);
> > +                     dma_async_issue_pending(pair->desc[OUT]->chan);
> > +             }
> >
> > -     asrc->m2m_start(pair);
> > +             asrc->m2m_start(pair);
> > +     }
> >
> >       if (!wait_for_completion_interruptible_timeout(&pair->complete[IN], 10 * HZ)) {
> >               dev_err(dev, "out DMA task timeout\n");
> > --
> > 2.34.1
> >