ASoC: fsl_esai: Add spin lock to protect reset, stop and start

xrun may happen at the end of stream, the
trigger->fsl_esai_trigger_stop maybe called in the middle of
fsl_esai_hw_reset, this may cause esai in wrong state
after stop, and there may be endless xrun interrupt.

This issue may also happen with trigger->fsl_esai_trigger_start.

So Add spin lock to lock those functions.

Fixes: 7ccafa2b38 ("ASoC: fsl_esai: recover the channel swap after xrun")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/52e92c4221a83e39a84a6cd92fc3d5479b44894c.1572252321.git.shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_esai.c

@@ -33,6 +33,7 @@
  * @fsysclk: system clock source to derive HCK, SCK and FS
  * @spbaclk: SPBA clock (optional, depending on SoC design)
  * @task: tasklet to handle the reset operation
+ * @lock: spin lock between hw_reset() and trigger()
  * @fifo_depth: depth of tx/rx FIFO
  * @slot_width: width of each DAI slot
  * @slots: number of slots
@@ -56,6 +57,7 @@ struct fsl_esai {
 	struct clk *fsysclk;
 	struct clk *spbaclk;
 	struct tasklet_struct task;
+	spinlock_t lock; /* Protect hw_reset and trigger */
 	u32 fifo_depth;
 	u32 slot_width;
 	u32 slots;
@@ -676,8 +678,10 @@ static void fsl_esai_hw_reset(unsigned long arg)
 {
 	struct fsl_esai *esai_priv = (struct fsl_esai *)arg;
 	bool tx = true, rx = false, enabled[2];
+	unsigned long lock_flags;
 	u32 tfcr, rfcr;
 
+	spin_lock_irqsave(&esai_priv->lock, lock_flags);
 	/* Save the registers */
 	regmap_read(esai_priv->regmap, REG_ESAI_TFCR, &tfcr);
 	regmap_read(esai_priv->regmap, REG_ESAI_RFCR, &rfcr);
@@ -715,6 +719,8 @@ static void fsl_esai_hw_reset(unsigned long arg)
 		fsl_esai_trigger_start(esai_priv, tx);
 	if (enabled[rx])
 		fsl_esai_trigger_start(esai_priv, rx);
+
+	spin_unlock_irqrestore(&esai_priv->lock, lock_flags);
 }
 
 static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
@@ -722,6 +728,7 @@ static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
 {
 	struct fsl_esai *esai_priv = snd_soc_dai_get_drvdata(dai);
 	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
+	unsigned long lock_flags;
 
 	esai_priv->channels[tx] = substream->runtime->channels;
 
@@ -729,12 +736,16 @@ static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		spin_lock_irqsave(&esai_priv->lock, lock_flags);
 		fsl_esai_trigger_start(esai_priv, tx);
+		spin_unlock_irqrestore(&esai_priv->lock, lock_flags);
 		break;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+		spin_lock_irqsave(&esai_priv->lock, lock_flags);
 		fsl_esai_trigger_stop(esai_priv, tx);
+		spin_unlock_irqrestore(&esai_priv->lock, lock_flags);
 		break;
 	default:
 		return -EINVAL;
@@ -1002,6 +1013,7 @@ static int fsl_esai_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&pdev->dev, esai_priv);
 
+	spin_lock_init(&esai_priv->lock);
 	ret = fsl_esai_hw_init(esai_priv);
 	if (ret)
 		return ret;