801-audio-0012-MLK-9974-ASoC-fsl_sai-There-is-underrun-detected-in-.patch

From 2a7fa96feddb63d36d64336a994dc4132e8a5cd4 Mon Sep 17 00:00:00 2001
From: Shengjiu Wang <shengjiu.wang@freescale.com>
Date: Mon, 29 Dec 2014 13:40:08 +0800
Subject: [PATCH] MLK-9974: ASoC: fsl_sai: There is underrun detected in the
 beginning sometimes

Write initial words to SAI FIFO to reduce underrun error

Signed-off-by: Shengjiu Wang <shengjiu.wang@freescale.com>
(cherry picked from commit 7ba8ae883d84540fac5ed4147d124399537bc0b3)
(cherry picked from commit f4435f35aa2a97551d2c4a12ca316c354a880f85)
---
 sound/soc/fsl/fsl_sai.c | 7 +++++++
 1 file changed, 7 insertions(+)

--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -506,7 +506,9 @@ static int fsl_sai_trigger(struct snd_pc
 {
 	struct fsl_sai *sai = snd_soc_dai_get_drvdata(cpu_dai);
 	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
+	u8 channels = substream->runtime->channels;
 	u32 xcsr, count = 100;
+	int i;
 
 	/*
 	 * Asynchronous mode: Clear SYNC for both Tx and Rx.
@@ -529,6 +531,11 @@ static int fsl_sai_trigger(struct snd_pc
 		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,