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Subject[PATCH] ASoC: fsl_sai: Fix noise when using EDMA
Date
From: Mihai Serban <mihai.serban@nxp.com>

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.

Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Mihai Serban <mihai.serban@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
---
sound/soc/fsl/fsl_sai.c | 15 +++++++++++++++
sound/soc/fsl/fsl_sai.h | 1 +
2 files changed, 16 insertions(+)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index 728307acab90..fe126029f4e3 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -612,6 +612,16 @@ static int fsl_sai_startup(struct snd_pcm_substream *substream,
FSL_SAI_CR3_TRCE_MASK,
FSL_SAI_CR3_TRCE);

+ /*
+ * some DMA controllers need period size to be a multiple of
+ * tx/rx maxburst
+ */
+ if (sai->soc_data->use_constraint_period_size)
+ 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);

@@ -1011,30 +1021,35 @@ static const struct fsl_sai_soc_data fsl_sai_vf610_data = {
.use_imx_pcm = false,
.fifo_depth = 32,
.reg_offset = 0,
+ .use_constraint_period_size = false,
};

static const struct fsl_sai_soc_data fsl_sai_imx6sx_data = {
.use_imx_pcm = true,
.fifo_depth = 32,
.reg_offset = 0,
+ .use_constraint_period_size = false,
};

static const struct fsl_sai_soc_data fsl_sai_imx7ulp_data = {
.use_imx_pcm = true,
.fifo_depth = 16,
.reg_offset = 8,
+ .use_constraint_period_size = false,
};

static const struct fsl_sai_soc_data fsl_sai_imx8mq_data = {
.use_imx_pcm = true,
.fifo_depth = 128,
.reg_offset = 8,
+ .use_constraint_period_size = false,
};

static const struct fsl_sai_soc_data fsl_sai_imx8qm_data = {
.use_imx_pcm = true,
.fifo_depth = 64,
.reg_offset = 0,
+ .use_constraint_period_size = true,
};

static const struct of_device_id fsl_sai_ids[] = {
diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
index b89b0ca26053..3a3f6f8e5595 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_constraint_period_size;
unsigned int fifo_depth;
unsigned int reg_offset;
};
--
2.17.1
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