[PATCH] ASoC: fsl_asrc_dma: fix eDMA maxburst misalignment with channel count

[PATCH] ASoC: fsl_asrc_dma: fix eDMA maxburst misalignment with channel count

[shengjiu.wang]

From: Shengjiu Wang <shengjiu.wang@nxp.com>

The back-end consumes data in units of the number of channels. When the
maxburst value is not evenly divisible by the channel count, the DMA
transfer length does not align with the FIFO frame boundary, causing
wrong data to be copied and audible noise at the end of the stream.

This is specific to eDMA: eDMA only responds to DMA requests from the
back-end, whereas SDMA handles requests from both the front-end and the
back-end and is not affected.

For eDMA, when the back-end maxburst is not evenly divisible by the
channel count, align it to the nearest valid boundary:
- If maxburst >= channel count, override to the channel count so each
  transfer corresponds to exactly one audio frame.
- If maxburst < channel count, override to 1 to avoid partial-frame
  transfers.

Retain the original maxburst for SDMA or when it already aligns with
the channel count.

Fixes: c05f10f28ef6 ("ASoC: fsl_asrc: Add support for imx8qm & imx8qxp")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 sound/soc/fsl/fsl_asrc_dma.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
index 5aa96af994c4..38f2b7c63133 100644
--- a/sound/soc/fsl/fsl_asrc_dma.c
+++ b/sound/soc/fsl/fsl_asrc_dma.c
@@ -288,6 +288,26 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	config_be.dst_addr_width = buswidth;
 	config_be.dst_maxburst = dma_params_be->maxburst;
 
+	/*
+	 * For eDMA, the back-end may report a maxburst size that is not evenly
+	 * divisible by the channel count. This causes the DMA transfer length
+	 * to misalign with the FIFO boundary, resulting in wrong data and
+	 * audible noise. Align maxburst to the nearest valid boundary:
+	 * - If maxburst >= channel count, override to the channel count so
+	 *   each transfer equals exactly one audio frame.
+	 * - If maxburst < channel count, override to 1 to avoid partial-frame
+	 *   transfers.
+	 */
+	if (asrc->use_edma && (dma_params_be->maxburst % params_channels(params))) {
+		if (dma_params_be->maxburst >= params_channels(params)) {
+			config_be.src_maxburst = params_channels(params);
+			config_be.dst_maxburst = params_channels(params);
+		} else {
+			config_be.src_maxburst = 1;
+			config_be.dst_maxburst = 1;
+		}
+	}
+
 	memset(&audio_config, 0, sizeof(audio_config));
 	config_be.peripheral_config = &audio_config;
 	config_be.peripheral_size  = sizeof(audio_config);
-- 
2.34.1

Re: [PATCH] ASoC: fsl_asrc_dma: fix eDMA maxburst misalignment with channel count

[Mark Brown]

On Thu, 25 Jun 2026 18:24:16 +0800, shengjiu.wang@oss.nxp.com wrote:
> ASoC: fsl_asrc_dma: fix eDMA maxburst misalignment with channel count

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.2

Thanks!

[1/1] ASoC: fsl_asrc_dma: fix eDMA maxburst misalignment with channel count
      https://git.kernel.org/broonie/sound/c/cf6f56990ea2

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark