linux-kernel - [PATCH 2/3] ASoC: fsl_sai: Don't reset FIFO until TE/RE bit is unset

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Date:	Wed, 23 Jul 2014 19:23:39 +0800
From:	Nicolin Chen <nicoleotsuka@...il.com>
To:	<broonie@...nel.org>
CC:	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<alsa-devel@...a-project.org>, <timur@...i.org>,
	<Li.Xiubo@...escale.com>, <b42378@...escale.com>,
	<b02247@...escale.com>
Subject: [PATCH 2/3] ASoC: fsl_sai: Don't reset FIFO until TE/RE bit is unset

From: Nicolin Chen <Guangyu.Chen@...escale.com>

TE/RE bit of T/RCSR will remain set untill the current frame is physically
finished. The FIFO reset operation should wait this bit's totally cleared
rather than ignoring its status which might cause TE/RE disabling failed.

This patch adds delay and timeout to wait for its completion before FIFO
reset.

Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
---
 sound/soc/fsl/fsl_sai.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index a437899..a79a9b0 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -327,7 +327,7 @@ 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;
-	u32 xcsr;
+	u32 xcsr, count = 100;
 
 	/*
 	 * The transmitter bit clock and frame sync are to be
@@ -369,11 +369,20 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 		if (!(xcsr & FSL_SAI_CSR_FRDE)) {
 			/* Disable both directions and reset their FIFOs */
 			regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
-					   FSL_SAI_CSR_TERE | FSL_SAI_CSR_FR,
-					   FSL_SAI_CSR_FR);
+					   FSL_SAI_CSR_TERE, 0);
 			regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
-					   FSL_SAI_CSR_TERE | FSL_SAI_CSR_FR,
-					   FSL_SAI_CSR_FR);
+					   FSL_SAI_CSR_TERE, 0);
+
+			/* TERE will remain set till the end of current frame */
+			do {
+				udelay(10);
+				regmap_read(sai->regmap, FSL_SAI_xCSR(tx), &xcsr);
+			} while (--count && xcsr & FSL_SAI_CSR_TERE);
+
+			regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
+					   FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
+			regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
+					   FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
 		}
 		break;
 	default:
-- 
1.8.4

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