ASoC: fsl_esai: recover the channel swap after xrun

There is chip errata ERR008000, the reference doc is
(https://www.nxp.com/docs/en/errata/IMX6DQCE.pdf),

The issue is "While using ESAI transmit or receive and
an underrun/overrun happens, channel swap may occur.
The only recovery mechanism is to reset the ESAI."

This issue exist in imx3/imx5/imx6(partial) series.

In this commit add a tasklet to handle reset of ESAI
after xrun happens to recover the channel swap.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/326035cb99975361699d9ed748054b08bc06a341.1562842206.git.shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: TE-N-ShengjiuWang

sound/soc/fsl/fsl_esai.c

@@ -32,6 +32,7 @@
  * @extalclk: esai clock source to derive HCK, SCK and FS
  * @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
  * @fifo_depth: depth of tx/rx FIFO
  * @slot_width: width of each DAI slot
  * @slots: number of slots
@@ -42,6 +43,7 @@
  * @sck_div: if using PSR/PM dividers for SCKx clock
  * @slave_mode: if fully using DAI slave mode
  * @synchronous: if using tx/rx synchronous mode
+ * @reset_at_xrun: flags for enable reset operaton
  * @name: driver name
  */
 struct fsl_esai {
@@ -53,6 +55,7 @@ struct fsl_esai {
 	struct clk *extalclk;
 	struct clk *fsysclk;
 	struct clk *spbaclk;
+	struct tasklet_struct task;
 	u32 fifo_depth;
 	u32 slot_width;
 	u32 slots;
@@ -65,6 +68,7 @@ struct fsl_esai {
 	bool sck_div[2];
 	bool slave_mode;
 	bool synchronous;
+	bool reset_at_xrun;
 	char name[32];
 };
 
@@ -73,8 +77,16 @@ static irqreturn_t esai_isr(int irq, void *devid)
 	struct fsl_esai *esai_priv = (struct fsl_esai *)devid;
 	struct platform_device *pdev = esai_priv->pdev;
 	u32 esr;
+	u32 saisr;
 
 	regmap_read(esai_priv->regmap, REG_ESAI_ESR, &esr);
+	regmap_read(esai_priv->regmap, REG_ESAI_SAISR, &saisr);
+
+	if ((saisr & (ESAI_SAISR_TUE | ESAI_SAISR_ROE)) &&
+	    esai_priv->reset_at_xrun) {
+		dev_dbg(&pdev->dev, "reset module for xrun\n");
+		tasklet_schedule(&esai_priv->task);
+	}
 
 	if (esr & ESAI_ESR_TINIT_MASK)
 		dev_dbg(&pdev->dev, "isr: Transmission Initialized\n");
@@ -635,10 +647,17 @@ static void fsl_esai_trigger_start(struct fsl_esai *esai_priv, bool tx)
 			   ESAI_xSMB_xS_MASK, ESAI_xSMB_xS(mask));
 	regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMA(tx),
 			   ESAI_xSMA_xS_MASK, ESAI_xSMA_xS(mask));
+
+	/* Enable Exception interrupt */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
+			   ESAI_xCR_xEIE_MASK, ESAI_xCR_xEIE);
 }
 
 static void fsl_esai_trigger_stop(struct fsl_esai *esai_priv, bool tx)
 {
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
+			   ESAI_xCR_xEIE_MASK, 0);
+
 	regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
 			   tx ? ESAI_xCR_TE_MASK : ESAI_xCR_RE_MASK, 0);
 	regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMA(tx),
@@ -653,6 +672,51 @@ static void fsl_esai_trigger_stop(struct fsl_esai *esai_priv, bool tx)
 			   ESAI_xFCR_xFR, 0);
 }
 
+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];
+	u32 tfcr, rfcr;
+
+	/* Save the registers */
+	regmap_read(esai_priv->regmap, REG_ESAI_TFCR, &tfcr);
+	regmap_read(esai_priv->regmap, REG_ESAI_RFCR, &rfcr);
+	enabled[tx] = tfcr & ESAI_xFCR_xFEN;
+	enabled[rx] = rfcr & ESAI_xFCR_xFEN;
+
+	/* Stop the tx & rx */
+	fsl_esai_trigger_stop(esai_priv, tx);
+	fsl_esai_trigger_stop(esai_priv, rx);
+
+	/* Reset the esai, and ignore return value */
+	fsl_esai_hw_init(esai_priv);
+
+	/* Enforce ESAI personal resets for both TX and RX */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_TCR,
+			   ESAI_xCR_xPR_MASK, ESAI_xCR_xPR);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_RCR,
+			   ESAI_xCR_xPR_MASK, ESAI_xCR_xPR);
+
+	/* Restore registers by regcache_sync, and ignore return value */
+	fsl_esai_register_restore(esai_priv);
+
+	/* Remove ESAI personal resets by configuring PCRC and PRRC also */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_TCR,
+			   ESAI_xCR_xPR_MASK, 0);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_RCR,
+			   ESAI_xCR_xPR_MASK, 0);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_PRRC,
+			   ESAI_PRRC_PDC_MASK, ESAI_PRRC_PDC(ESAI_GPIO));
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_PCRC,
+			   ESAI_PCRC_PC_MASK, ESAI_PCRC_PC(ESAI_GPIO));
+
+	/* Restart tx / rx, if they already enabled */
+	if (enabled[tx])
+		fsl_esai_trigger_start(esai_priv, tx);
+	if (enabled[rx])
+		fsl_esai_trigger_start(esai_priv, rx);
+}
+
 static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
 			    struct snd_soc_dai *dai)
 {
@@ -857,6 +921,10 @@ static int fsl_esai_probe(struct platform_device *pdev)
 	esai_priv->pdev = pdev;
 	snprintf(esai_priv->name, sizeof(esai_priv->name), "%pOFn", np);
 
+	if (of_device_is_compatible(np, "fsl,vf610-esai") ||
+	    of_device_is_compatible(np, "fsl,imx35-esai"))
+		esai_priv->reset_at_xrun = true;
+
 	/* Get the addresses and IRQ */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	regs = devm_ioremap_resource(&pdev->dev, res);
@@ -956,6 +1024,9 @@ static int fsl_esai_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	tasklet_init(&esai_priv->task, fsl_esai_hw_reset,
+		     (unsigned long)esai_priv);
+
 	pm_runtime_enable(&pdev->dev);
 
 	regcache_cache_only(esai_priv->regmap, true);
@@ -969,7 +1040,10 @@ static int fsl_esai_probe(struct platform_device *pdev)
 
 static int fsl_esai_remove(struct platform_device *pdev)
 {
+	struct fsl_esai *esai_priv = platform_get_drvdata(pdev);
+
 	pm_runtime_disable(&pdev->dev);
+	tasklet_kill(&esai_priv->task);
 
 	return 0;
 }