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Message-ID: <aXzDlScEXfmUys32@lizhi-Precision-Tower-5810>
Date: Fri, 30 Jan 2026 09:43:33 -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 v2 3/4] ASoC: fsl_asrc_m2m: Start ASRC before DMA device
for M2M
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@....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()
> +
> + 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);
Frank
>
> if (!wait_for_completion_interruptible_timeout(&pair->complete[IN], 10 * HZ)) {
> dev_err(dev, "out DMA task timeout\n");
> --
> 2.34.1
>
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