openwrt/target/linux/layerscape/patches-5.4/801-audio-0028-MLK-15927-1-ASoC-fsl_sai-Fix-noise-when-using-EDMA.patch

From 3b671c297cff1ba5f5c3e089ffa82523eca3c598 Mon Sep 17 00:00:00 2001
From: Mihai Serban <mihai.serban@nxp.com>
Date: Fri, 7 Jul 2017 15:09:51 +0300
Subject: [PATCH] MLK-15927-1: 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.

This is based on a similar patch we have for ESAI:
commit bd3f3eb2a37c
("MLK-15109-2: ASoC: fsl_esai: add constrain_period_size")

Signed-off-by: Mihai Serban <mihai.serban@nxp.com>
Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 sound/soc/fsl/fsl_sai.c | 23 +++++++++++++++++++++++
 sound/soc/fsl/fsl_sai.h |  2 ++
 2 files changed, 25 insertions(+)

--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -35,6 +35,7 @@ static struct fsl_sai_soc_data fsl_sai_v
 	.fifos = 1,
 	.fifo_depth = 32,
 	.flags = 0,
+	.constrain_period_size = false,
 };
 
 static struct fsl_sai_soc_data fsl_sai_imx6sx = {
@@ -44,6 +45,7 @@ static struct fsl_sai_soc_data fsl_sai_i
 	.fifo_depth = 32,
 	.flags = 0,
 	.reg_offset = 0,
+	.constrain_period_size = false,
 };
 
 static struct fsl_sai_soc_data fsl_sai_imx6ul = {
@@ -53,6 +55,7 @@ static struct fsl_sai_soc_data fsl_sai_i
 	.fifo_depth = 32,
 	.flags = 0,
 	.reg_offset = 0,
+	.constrain_period_size = false,
 };
 
 static struct fsl_sai_soc_data fsl_sai_imx7ulp = {
@@ -62,6 +65,7 @@ static struct fsl_sai_soc_data fsl_sai_i
 	.fifo_depth = 16,
 	.flags = SAI_FLAG_PMQOS,
 	.reg_offset = 0,
+	.constrain_period_size = false,
 };
 
 static struct fsl_sai_soc_data fsl_sai_imx8mq = {
@@ -71,6 +75,17 @@ static struct fsl_sai_soc_data fsl_sai_i
 	.fifo_depth = 32,
 	.flags = 0,
 	.reg_offset = 8,
+	.constrain_period_size = false,
+};
+
+static struct fsl_sai_soc_data fsl_sai_imx8qm = {
+	.imx = true,
+	.dataline = 0x3,
+	.fifos = 1,
+	.fifo_depth = 32,
+	.flags = 0,
+	.reg_offset = 0,
+	.constrain_period_size = true,
 };
 
 static const unsigned int fsl_sai_rates[] = {
@@ -692,6 +707,13 @@ static int fsl_sai_startup(struct snd_pc
 			   FSL_SAI_CR3_TRCE_MASK,
 			   FSL_SAI_CR3_TRCE(sai->dataline[tx]));
 
+	/* EDMA engine needs periods of size multiple of tx/rx maxburst */
+	if (sai->soc->constrain_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);
 
@@ -914,6 +936,7 @@ static const struct of_device_id fsl_sai
 	{ .compatible = "fsl,imx6ul-sai", .data = &fsl_sai_imx6ul },
 	{ .compatible = "fsl,imx7ulp-sai", .data = &fsl_sai_imx7ulp },
 	{ .compatible = "fsl,imx8mq-sai", .data = &fsl_sai_imx8mq },
+	{ .compatible = "fsl,imx8qm-sai", .data = &fsl_sai_imx8qm },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, fsl_sai_ids);
--- a/sound/soc/fsl/fsl_sai.h
+++ b/sound/soc/fsl/fsl_sai.h
@@ -147,6 +147,8 @@ struct fsl_sai_soc_data {
 	unsigned int flags;
 	unsigned char reg_offset;
 	bool imx;
+	/* True for EDMA because it needs period size multiple of maxburst */
+	bool constrain_period_size;
 };
 
 struct fsl_sai {