commit e75f4940e8ad0dd76527302a10c06b58bf7eb590
author Mihai Serban <mihai.serban@nxp.com> Fri Sep 13 22:28:05 2019 +0300
committer Mark Brown <broonie@kernel.org> Tue Sep 17 16:56:19 2019 +0100
tree 4aa03850072854d477181319f253cee00e92c9f0
parent fca11622d600228bec405456f41590155b3a3eca

ASoC: fsl_sai: Fix noise when using EDMA

EDMA requires the period size to be multiple of maxburst. Otherwise the
remaining bytes are not transferred and thus noise is produced.

We can handle this issue by adding a constraint on
SNDRV_PCM_HW_PARAM_PERIOD_SIZE to be multiple of tx/rx maxburst value.

Signed-off-by: Mihai Serban <mihai.serban@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/20190913192807.8423-2-daniel.baluta@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_sai.c

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index ef0b746..b517e4b 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -628,6 +628,16 @@ static int fsl_sai_startup(struct snd_pcm_substream *substream,
 			   FSL_SAI_CR3_TRCE_MASK,
 			   FSL_SAI_CR3_TRCE);
 
+	/*
+	 * EDMA controller needs period size to be a multiple of
+	 * tx/rx maxburst
+	 */
+	if (sai->soc_data->use_edma)
+		snd_pcm_hw_constraint_step(substream->runtime, 0,
+					   SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
+					   tx ? sai->dma_params_tx.maxburst :
+					   sai->dma_params_rx.maxburst);
+
 	ret = snd_pcm_hw_constraint_list(substream->runtime, 0,
 			SNDRV_PCM_HW_PARAM_RATE, &fsl_sai_rate_constraints);
 
@@ -1026,30 +1036,35 @@ static int fsl_sai_remove(struct platform_device *pdev)
 
 static const struct fsl_sai_soc_data fsl_sai_vf610_data = {
 	.use_imx_pcm = false,
+	.use_edma = false,
 	.fifo_depth = 32,
 	.reg_offset = 0,
 };
 
 static const struct fsl_sai_soc_data fsl_sai_imx6sx_data = {
 	.use_imx_pcm = true,
+	.use_edma = false,
 	.fifo_depth = 32,
 	.reg_offset = 0,
 };
 
 static const struct fsl_sai_soc_data fsl_sai_imx7ulp_data = {
 	.use_imx_pcm = true,
+	.use_edma = false,
 	.fifo_depth = 16,
 	.reg_offset = 8,
 };
 
 static const struct fsl_sai_soc_data fsl_sai_imx8mq_data = {
 	.use_imx_pcm = true,
+	.use_edma = false,
 	.fifo_depth = 128,
 	.reg_offset = 8,
 };
 
 static const struct fsl_sai_soc_data fsl_sai_imx8qm_data = {
 	.use_imx_pcm = true,
+	.use_edma = true,
 	.fifo_depth = 64,
 	.reg_offset = 0,
 };

sound/soc/fsl/fsl_sai.h

diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
index b12cb57..76b15de 100644
--- a/sound/soc/fsl/fsl_sai.h
+++ b/sound/soc/fsl/fsl_sai.h
@@ -157,6 +157,7 @@
 
 struct fsl_sai_soc_data {
 	bool use_imx_pcm;
+	bool use_edma;
 	unsigned int fifo_depth;
 	unsigned int reg_offset;
 };