Re: [PATCH v2 3/4] ASoC: fsl_asrc_m2m: Start ASRC before DMA device for M2M

Shengjiu Wang
2026-02-02T09:44:38Z

On Fri, Jan 30, 2026 at 10:43 PM Frank Li <Frank.li@nxp.com> wrote:
>
> On Fri, Jan 30, 2026 at 01:43:29PM +0800, Shengjiu Wang wrote:
> > 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@nxp.com>
> > ---
> > sound/soc/fsl/fsl_asrc.c | 25 +++++++++++++++++++++++++
> > sound/soc/fsl/fsl_asrc.h | 2 ++
> > sound/soc/fsl/fsl_asrc_common.h | 4 ++++
> > sound/soc/fsl/fsl_asrc_m2m.c | 29 +++++++++++++++++++++--------
> > 4 files changed, 52 insertions(+), 8 deletions(-)
> >
> > diff --git a/sound/soc/fsl/fsl_asrc.c b/sound/soc/fsl/fsl_asrc.c
> > index 5846a2b1f73c..2374577c13f9 100644
> > --- a/sound/soc/fsl/fsl_asrc.c
> > +++ b/sound/soc/fsl/fsl_asrc.c
> > @@ -1084,6 +1084,28 @@ static unsigned int fsl_asrc_get_output_fifo_size(struct fsl_asrc_pair *pair)
> > return val >> ASRFSTi_OUTPUT_FIFO_SHIFT;
> > }
> >
> > +static bool fsl_asrc_m2m_output_ready(struct fsl_asrc_pair *pair)
> > +{
> > + struct fsl_asrc *asrc = pair->asrc;
> > + enum asrc_pair_index index = pair->index;
> > + int retry = 1000;
> > + u32 val;
> > +
> > + /* Check output fifo status if it exceeds the watermark. */
> > + do {
> > + regmap_read(asrc->regmap, REG_ASRFST(index), &val);
> > + val &= ASRFSTi_OUTPUT_FIFO_MASK;
> > + val = val >> ASRFSTi_OUTPUT_FIFO_SHIFT;
> > + } while (val < ASRC_M2M_OUTPUTFIFO_WML && --retry);
>
> use regmap_read_poll_timeout()

Ok, will update it.

>
> > +
> > + if (!retry) {
> > + pair_warn("output is not ready\n");
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > static int fsl_asrc_m2m_prepare(struct fsl_asrc_pair *pair)
> > {
> > struct fsl_asrc_pair_priv *pair_priv = pair->private;
> > @@ -1281,6 +1303,7 @@ static int fsl_asrc_probe(struct platform_device *pdev)
> >
> > asrc_priv->soc = of_device_get_match_data(&pdev->dev);
> > asrc->use_edma = asrc_priv->soc->use_edma;
> > + asrc->start_before_dma = asrc_priv->soc->start_before_dma;
> > asrc->get_dma_channel = fsl_asrc_get_dma_channel;
> > asrc->request_pair = fsl_asrc_request_pair;
> > asrc->release_pair = fsl_asrc_release_pair;
> > @@ -1295,6 +1318,7 @@ static int fsl_asrc_probe(struct platform_device *pdev)
> > asrc->m2m_get_maxburst = fsl_asrc_m2m_get_maxburst;
> > asrc->m2m_pair_resume = fsl_asrc_m2m_pair_resume;
> > asrc->m2m_get_cap = fsl_asrc_m2m_get_cap;
> > + asrc->m2m_output_ready = fsl_asrc_m2m_output_ready;
> >
> > if (of_device_is_compatible(np, "fsl,imx35-asrc")) {
> > asrc_priv->clk_map[IN] = input_clk_map_imx35;
> > @@ -1565,6 +1589,7 @@ static const struct fsl_asrc_soc_data fsl_asrc_imx8qxp_data = {
> > static const struct fsl_asrc_soc_data fsl_asrc_imx952_data = {
> > .use_edma = true,
> > .channel_bits = 4,
> > + .start_before_dma = true,
> > };
> >
> > static const struct of_device_id fsl_asrc_ids[] = {
> > diff --git a/sound/soc/fsl/fsl_asrc.h b/sound/soc/fsl/fsl_asrc.h
> > index 2f67b085de24..1be93148a879 100644
> > --- a/sound/soc/fsl/fsl_asrc.h
> > +++ b/sound/soc/fsl/fsl_asrc.h
> > @@ -446,10 +446,12 @@ struct dma_block {
> > *
> > * @use_edma: using edma as dma device or not
> > * @channel_bits: width of ASRCNCR register for each pair
> > + * @start_before_dma: start asrc before dma
> > */
> > struct fsl_asrc_soc_data {
> > bool use_edma;
> > unsigned int channel_bits;
> > + bool start_before_dma;
> > };
> >
> > /**
> > diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h
> > index 0cd595b0f629..c8a1a2b5915d 100644
> > --- a/sound/soc/fsl/fsl_asrc_common.h
> > +++ b/sound/soc/fsl/fsl_asrc_common.h
> > @@ -107,6 +107,7 @@ struct fsl_asrc_pair {
> > * @asrc_rate: default sample rate for ASoC Back-Ends
> > * @asrc_format: default sample format for ASoC Back-Ends
> > * @use_edma: edma is used
> > + * @start_before_dma: start asrc before dma
> > * @get_dma_channel: function pointer
> > * @request_pair: function pointer
> > * @release_pair: function pointer
> > @@ -116,6 +117,7 @@ struct fsl_asrc_pair {
> > * @m2m_start: function pointer
> > * @m2m_unprepare: function pointer
> > * @m2m_stop: function pointer
> > + * @m2m_output_ready: function pointer, check output fifo ready or not
> > * @m2m_calc_out_len: function pointer
> > * @m2m_get_maxburst: function pointer
> > * @m2m_pair_suspend: function pointer
> > @@ -143,6 +145,7 @@ struct fsl_asrc {
> > int asrc_rate;
> > snd_pcm_format_t asrc_format;
> > bool use_edma;
> > + bool start_before_dma;
> >
> > struct dma_chan *(*get_dma_channel)(struct fsl_asrc_pair *pair, bool dir);
> > int (*request_pair)(int channels, struct fsl_asrc_pair *pair);
> > @@ -154,6 +157,7 @@ struct fsl_asrc {
> > int (*m2m_start)(struct fsl_asrc_pair *pair);
> > int (*m2m_unprepare)(struct fsl_asrc_pair *pair);
> > int (*m2m_stop)(struct fsl_asrc_pair *pair);
> > + bool (*m2m_output_ready)(struct fsl_asrc_pair *pair);
> >
> > int (*m2m_calc_out_len)(struct fsl_asrc_pair *pair, int input_buffer_length);
> > int (*m2m_get_maxburst)(u8 dir, struct fsl_asrc_pair *pair);
> > 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);
> > + /* 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 really like start_before_dma, move common part no change
>
> if (start_before_dma)
> asrc->m2m_start(pair);
>
> ....
>
> if (!start_before_dma)
> asrc->m2m_start(pair);

Ok, will update it.

best regards
Shengjiu Wang
>
> Frank
> >
> > if (!wait_for_completion_interruptible_timeout(&pair->complete[IN], 10 * HZ)) {
> > dev_err(dev, "out DMA task timeout\n");
> > --
> > 2.34.1
> >