linux-kernel - [PATCH] ASoC: fsl: sai: Reduce underrun when stream starts

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Message-ID: <20190308160933.29899-1-daniel.baluta@nxp.com>
Date:   Fri, 8 Mar 2019 16:09:53 +0000
From:   Daniel Baluta <daniel.baluta@....com>
To:     "broonie@...nel.org" <broonie@...nel.org>
CC:     "tiwai@...e.com" <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "festevam@...il.com" <festevam@...il.com>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "nicoleotsuka@...il.com" <nicoleotsuka@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "S.j. Wang" <shengjiu.wang@....com>,
        Daniel Baluta <daniel.baluta@....com>
Subject: [PATCH] ASoC: fsl: sai: Reduce underrun when stream starts

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

Write initial words into SAI FIFO to reduce the underrun
error.

Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
Signed-off-by: Daniel Baluta <daniel.baluta@....com>
---
 sound/soc/fsl/fsl_sai.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index db9e0872f73d..99edbba4e8fa 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -503,7 +503,9 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 {
 	struct fsl_sai *sai = snd_soc_dai_get_drvdata(cpu_dai);
 	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
+	unsigned int channels = substream->runtime->channels;
 	u32 xcsr, count = 100;
+	int i;
 
 	/*
 	 * Asynchronous mode: Clear SYNC for both Tx and Rx.
@@ -526,6 +528,11 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 		regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx),
 				   FSL_SAI_CSR_FRDE, FSL_SAI_CSR_FRDE);
 
+		for (i = 0; tx && i < channels; i++)
+			regmap_write(sai->regmap, FSL_SAI_TDR, 0x0);
+		if (tx)
+			udelay(10);
+
 		regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
 				   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
 		regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
-- 
2.17.1