[PATCH V3 0/2] recover the channel swap after xrun

[PATCH V3 0/2] recover the channel swap after xrun

[shengjiu.wang]

From: Shengjiu Wang <shengjiu.wang@nxp.com>

recover the channel swap after xrun

Shengjiu Wang (2):
  ASoC: fsl_esai: Wrap some operations to be functions
  ASoC: fsl_esai: recover the channel swap after xrun

 sound/soc/fsl/fsl_esai.c | 270 ++++++++++++++++++++++++++++-----------
 1 file changed, 197 insertions(+), 73 deletions(-)

Changes in V3
- update code sytle.

Changes in v2
- add one patch for wrap operations to functions.
- fix some coding style issue

-- 
2.21.0

[PATCH V3 1/2] ASoC: fsl_esai: Wrap some operations to be functions

[shengjiu.wang]

From: Shengjiu Wang <shengjiu.wang@nxp.com>

Extract the operation to be functions, to improve the
readability.

In this patch, fsl_esai_hw_init, fsl_esai_register_restore,
fsl_esai_trigger_start and fsl_esai_trigger_stop are
extracted.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
 sound/soc/fsl/fsl_esai.c | 192 ++++++++++++++++++++++++---------------
 1 file changed, 119 insertions(+), 73 deletions(-)

diff --git a/sound/soc/fsl/fsl_esai.c b/sound/soc/fsl/fsl_esai.c
index 10d2210c91ef..ab460d6d7432 100644
--- a/sound/soc/fsl/fsl_esai.c
+++ b/sound/soc/fsl/fsl_esai.c
@@ -35,6 +35,7 @@
  * @fifo_depth: depth of tx/rx FIFO
  * @slot_width: width of each DAI slot
  * @slots: number of slots
+ * @channels: channel num for tx or rx
  * @hck_rate: clock rate of desired HCKx clock
  * @sck_rate: clock rate of desired SCKx clock
  * @hck_dir: the direction of HCKx pads
@@ -57,6 +58,7 @@ struct fsl_esai {
 	u32 slots;
 	u32 tx_mask;
 	u32 rx_mask;
+	u32 channels[2];
 	u32 hck_rate[2];
 	u32 sck_rate[2];
 	bool hck_dir[2];
@@ -543,64 +545,132 @@ static int fsl_esai_hw_params(struct snd_pcm_substream *substream,
 	return 0;
 }
 
-static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
-			    struct snd_soc_dai *dai)
+static int fsl_esai_hw_init(struct fsl_esai *esai_priv)
 {
-	struct fsl_esai *esai_priv = snd_soc_dai_get_drvdata(dai);
-	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
-	u8 i, channels = substream->runtime->channels;
+	struct platform_device *pdev = esai_priv->pdev;
+	int ret;
+
+	/* Reset ESAI unit */
+	ret = regmap_update_bits(esai_priv->regmap, REG_ESAI_ECR,
+				 ESAI_ECR_ESAIEN_MASK | ESAI_ECR_ERST_MASK,
+				 ESAI_ECR_ESAIEN | ESAI_ECR_ERST);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to reset ESAI: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * We need to enable ESAI so as to access some of its registers.
+	 * Otherwise, we would fail to dump regmap from user space.
+	 */
+	ret = regmap_update_bits(esai_priv->regmap, REG_ESAI_ECR,
+				 ESAI_ECR_ESAIEN_MASK | ESAI_ECR_ERST_MASK,
+				 ESAI_ECR_ESAIEN);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable ESAI: %d\n", ret);
+		return ret;
+	}
+
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_PRRC,
+			   ESAI_PRRC_PDC_MASK, 0);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_PCRC,
+			   ESAI_PCRC_PC_MASK, 0);
+
+	return 0;
+}
+
+static int fsl_esai_register_restore(struct fsl_esai *esai_priv)
+{
+	int ret;
+
+	/* FIFO reset for safety */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_TFCR,
+			   ESAI_xFCR_xFR, ESAI_xFCR_xFR);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_RFCR,
+			   ESAI_xFCR_xFR, ESAI_xFCR_xFR);
+
+	regcache_mark_dirty(esai_priv->regmap);
+	ret = regcache_sync(esai_priv->regmap);
+	if (ret)
+		return ret;
+
+	/* FIFO reset done */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_TFCR, ESAI_xFCR_xFR, 0);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_RFCR, ESAI_xFCR_xFR, 0);
+
+	return 0;
+}
+
+static void fsl_esai_trigger_start(struct fsl_esai *esai_priv, bool tx)
+{
+	u8 i, channels = esai_priv->channels[tx];
 	u32 pins = DIV_ROUND_UP(channels, esai_priv->slots);
 	u32 mask;
 
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
+			   ESAI_xFCR_xFEN_MASK, ESAI_xFCR_xFEN);
+
+	/* Write initial words reqiured by ESAI as normal procedure */
+	for (i = 0; tx && i < channels; i++)
+		regmap_write(esai_priv->regmap, REG_ESAI_ETDR, 0x0);
+
+	/*
+	 * When set the TE/RE in the end of enablement flow, there
+	 * will be channel swap issue for multi data line case.
+	 * In order to workaround this issue, we switch the bit
+	 * enablement sequence to below sequence
+	 * 1) clear the xSMB & xSMA: which is done in probe and
+	 *                           stop state.
+	 * 2) set TE/RE
+	 * 3) set xSMB
+	 * 4) set xSMA:  xSMA is the last one in this flow, which
+	 *               will trigger esai to start.
+	 */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
+			   tx ? ESAI_xCR_TE_MASK : ESAI_xCR_RE_MASK,
+			   tx ? ESAI_xCR_TE(pins) : ESAI_xCR_RE(pins));
+	mask = tx ? esai_priv->tx_mask : esai_priv->rx_mask;
+
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(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));
+}
+
+static void fsl_esai_trigger_stop(struct fsl_esai *esai_priv, bool tx)
+{
+	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),
+			   ESAI_xSMA_xS_MASK, 0);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(tx),
+			   ESAI_xSMB_xS_MASK, 0);
+
+	/* Disable and reset FIFO */
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
+			   ESAI_xFCR_xFR | ESAI_xFCR_xFEN, ESAI_xFCR_xFR);
+	regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
+			   ESAI_xFCR_xFR, 0);
+}
+
+static int fsl_esai_trigger(struct snd_pcm_substream *substream, int cmd,
+			    struct snd_soc_dai *dai)
+{
+	struct fsl_esai *esai_priv = snd_soc_dai_get_drvdata(dai);
+	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
+
+	esai_priv->channels[tx] = substream->runtime->channels;
+
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
-				   ESAI_xFCR_xFEN_MASK, ESAI_xFCR_xFEN);
-
-		/* Write initial words reqiured by ESAI as normal procedure */
-		for (i = 0; tx && i < channels; i++)
-			regmap_write(esai_priv->regmap, REG_ESAI_ETDR, 0x0);
-
-		/*
-		 * When set the TE/RE in the end of enablement flow, there
-		 * will be channel swap issue for multi data line case.
-		 * In order to workaround this issue, we switch the bit
-		 * enablement sequence to below sequence
-		 * 1) clear the xSMB & xSMA: which is done in probe and
-		 *                           stop state.
-		 * 2) set TE/RE
-		 * 3) set xSMB
-		 * 4) set xSMA:  xSMA is the last one in this flow, which
-		 *               will trigger esai to start.
-		 */
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xCR(tx),
-				   tx ? ESAI_xCR_TE_MASK : ESAI_xCR_RE_MASK,
-				   tx ? ESAI_xCR_TE(pins) : ESAI_xCR_RE(pins));
-		mask = tx ? esai_priv->tx_mask : esai_priv->rx_mask;
-
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(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));
-
+		fsl_esai_trigger_start(esai_priv, tx);
 		break;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		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),
-				   ESAI_xSMA_xS_MASK, 0);
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xSMB(tx),
-				   ESAI_xSMB_xS_MASK, 0);
-
-		/* Disable and reset FIFO */
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
-				   ESAI_xFCR_xFR | ESAI_xFCR_xFEN, ESAI_xFCR_xFR);
-		regmap_update_bits(esai_priv->regmap, REG_ESAI_xFCR(tx),
-				   ESAI_xFCR_xFR, 0);
+		fsl_esai_trigger_stop(esai_priv, tx);
 		break;
 	default:
 		return -EINVAL;
@@ -866,22 +936,9 @@ static int fsl_esai_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&pdev->dev, esai_priv);
 
-	/* Reset ESAI unit */
-	ret = regmap_write(esai_priv->regmap, REG_ESAI_ECR, ESAI_ECR_ERST);
-	if (ret) {
-		dev_err(&pdev->dev, "failed to reset ESAI: %d\n", ret);
+	ret = fsl_esai_hw_init(esai_priv);
+	if (ret)
 		return ret;
-	}
-
-	/*
-	 * We need to enable ESAI so as to access some of its registers.
-	 * Otherwise, we would fail to dump regmap from user space.
-	 */
-	ret = regmap_write(esai_priv->regmap, REG_ESAI_ECR, ESAI_ECR_ESAIEN);
-	if (ret) {
-		dev_err(&pdev->dev, "failed to enable ESAI: %d\n", ret);
-		return ret;
-	}
 
 	esai_priv->tx_mask = 0xFFFFFFFF;
 	esai_priv->rx_mask = 0xFFFFFFFF;
@@ -955,20 +1012,10 @@ static int fsl_esai_runtime_resume(struct device *dev)
 
 	regcache_cache_only(esai->regmap, false);
 
-	/* FIFO reset for safety */
-	regmap_update_bits(esai->regmap, REG_ESAI_TFCR,
-			   ESAI_xFCR_xFR, ESAI_xFCR_xFR);
-	regmap_update_bits(esai->regmap, REG_ESAI_RFCR,
-			   ESAI_xFCR_xFR, ESAI_xFCR_xFR);
-
-	ret = regcache_sync(esai->regmap);
+	ret = fsl_esai_register_restore(esai);
 	if (ret)
 		goto err_regcache_sync;
 
-	/* FIFO reset done */
-	regmap_update_bits(esai->regmap, REG_ESAI_TFCR, ESAI_xFCR_xFR, 0);
-	regmap_update_bits(esai->regmap, REG_ESAI_RFCR, ESAI_xFCR_xFR, 0);
-
 	return 0;
 
 err_regcache_sync:
@@ -991,7 +1038,6 @@ static int fsl_esai_runtime_suspend(struct device *dev)
 	struct fsl_esai *esai = dev_get_drvdata(dev);
 
 	regcache_cache_only(esai->regmap, true);
-	regcache_mark_dirty(esai->regmap);
 
 	if (!IS_ERR(esai->fsysclk))
 		clk_disable_unprepare(esai->fsysclk);
-- 
2.21.0

[PATCH V3 2/2] ASoC: fsl_esai: recover the channel swap after xrun

[shengjiu.wang]

From: Shengjiu Wang <shengjiu.wang@nxp.com>

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>
---
 sound/soc/fsl/fsl_esai.c | 78 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/sound/soc/fsl/fsl_esai.c b/sound/soc/fsl/fsl_esai.c
index ab460d6d7432..416bec424fd6 100644
--- a/sound/soc/fsl/fsl_esai.c
+++ b/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 +672,55 @@ 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;
+	u32 saisr, tfcr, rfcr;
+	bool tx = true, rx = false, enabled[2];
+
+	/* 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);
+
+	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);
+
+	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));
+
+	regmap_read(esai_priv->regmap, REG_ESAI_SAISR, &saisr);
+
+	/* 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 +925,10 @@ 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 +1028,9 @@ 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 +1044,10 @@ 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;
 }
-- 
2.21.0

Re: [PATCH V3 2/2] ASoC: fsl_esai: recover the channel swap after xrun

[Nicolin Chen]

Hi Shengjiu,

Mostly looks good to me, just some small comments.

On Mon, Jul 08, 2019 at 02:38:52PM +0800, shengjiu.wang@nxp.com wrote:
  
> +static void fsl_esai_hw_reset(unsigned long arg)
> +{
> +	struct fsl_esai *esai_priv = (struct fsl_esai *)arg;
> +	u32 saisr, tfcr, rfcr;
> +	bool tx = true, rx = false, enabled[2];

Could we swap the lines of u32 and bool? It'd look better.

> +	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);

Let's add a line of comments for these two:
	/* Enforce ESAI personal resets for both TX and RX */

> +	/*
> +	 * Restore registers by regcache_sync, and ignore
> +	 * return value
> +	 */

Could fit into single-line?

> +	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));

Could remove the blank line and add a line of comments:
	/* Remove ESAI personal resets by configuring PCRC and PRRC also */

Btw, I still feel this personal reset can be stuffed into one
of the wrapper functions. But let's keep this simple for now.

> +	regmap_read(esai_priv->regmap, REG_ESAI_SAISR, &saisr);

Why do we read saisr here? All its bits would get cleared by
the hardware reset. If it's a must to clear again, we should
add a line of comments to emphasize it.

Thank you