ASoC: fsl_sai: Reduce race condition during TE/RE enabling

For trigger start, we don't need to check if it's the first time to
enable TE/RE or second time. It doesn't hurt to enable them any way,
which in the meantime can reduce race condition for TE/RE enabling.

For trigger stop, we will definitely clear FRDE of current direction.
Thus the driver only needs to read the opposite one's.
Signed-off-by: NNicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

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 tcsr, rcsr;
+	u32 xcsr;
 
 	/*
 	 * The transmitter bit clock and frame sync are to be
@@ -338,9 +338,6 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 	regmap_update_bits(sai->regmap, FSL_SAI_RCR2, FSL_SAI_CR2_SYNC,
 			   FSL_SAI_CR2_SYNC);
 
-	regmap_read(sai->regmap, FSL_SAI_TCSR, &tcsr);
-	regmap_read(sai->regmap, FSL_SAI_RCSR, &rcsr);
-
 	/*
 	 * It is recommended that the transmitter is the last enabled
 	 * and the first disabled.
@@ -349,12 +346,10 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		if (!(tcsr & FSL_SAI_CSR_FRDE || rcsr & FSL_SAI_CSR_FRDE)) {
-			regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
-					   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
-			regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
-					   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
-		}
+		regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
+				   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
+		regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
+				   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
 
 		regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx),
 				   FSL_SAI_CSR_xIE_MASK, FSL_SAI_FLAGS);
@@ -370,7 +365,8 @@ static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
 				   FSL_SAI_CSR_xIE_MASK, 0);
 
 		/* Check if the opposite FRDE is also disabled */
-		if (!(tx ? rcsr & FSL_SAI_CSR_FRDE : tcsr & FSL_SAI_CSR_FRDE)) {
+		regmap_read(sai->regmap, FSL_SAI_xCSR(!tx), &xcsr);
+		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,