[09/12] i2c: qup: fix buffer overflow for multiple msg of maximum xfer len

Message ID 1517644697-30806-10-git-send-email-absahu@codeaurora.org
State New
Headers show
Series
  • Major code reorganization to make all i2c transfers working
Related show

Commit Message

Abhishek Sahu Feb. 3, 2018, 7:58 a.m.
The BAM mode requires buffer for start tag data and tx, rx SG
list. Currently, this is being taken for maximum transfer length
(65K). But an I2C transfer can have multiple messages and each
message can be of this maximum length so the buffer overflow will
happen in this case. Since increasing buffer length won’t be
feasible since an I2C transfer can contain any number of messages
so this patch does following changes to make i2c transfers working
for multiple messages case.

1. Calculate the required buffers for 2 maximum length messages
   (65K * 2).
2. Split the descriptor formation and descriptor scheduling.
   The idea is to fit as many messages in one DMA transfers for 65K
   threshold value (max_xfer_sg_len). Whenever the sg_cnt is
   crossing this, then schedule the BAM transfer and subsequent
   transfer will again start from zero.

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
---
 drivers/i2c/busses/i2c-qup.c | 199 +++++++++++++++++++++++++------------------
 1 file changed, 118 insertions(+), 81 deletions(-)

Comments

Sricharan R Feb. 16, 2018, 5:21 a.m. | #1
Hi Abhishek,

On 2/3/2018 1:28 PM, Abhishek Sahu wrote:
> The BAM mode requires buffer for start tag data and tx, rx SG
> list. Currently, this is being taken for maximum transfer length
> (65K). But an I2C transfer can have multiple messages and each
> message can be of this maximum length so the buffer overflow will
> happen in this case. Since increasing buffer length won’t be
> feasible since an I2C transfer can contain any number of messages
> so this patch does following changes to make i2c transfers working
> for multiple messages case.
> 
> 1. Calculate the required buffers for 2 maximum length messages
>    (65K * 2).
> 2. Split the descriptor formation and descriptor scheduling.
>    The idea is to fit as many messages in one DMA transfers for 65K
>    threshold value (max_xfer_sg_len). Whenever the sg_cnt is
>    crossing this, then schedule the BAM transfer and subsequent
>    transfer will again start from zero.
> 
> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
> ---
>  drivers/i2c/busses/i2c-qup.c | 199 +++++++++++++++++++++++++------------------
>  1 file changed, 118 insertions(+), 81 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> index 6df65ea..ba717bb 100644
> --- a/drivers/i2c/busses/i2c-qup.c
> +++ b/drivers/i2c/busses/i2c-qup.c
> @@ -155,6 +155,7 @@ struct qup_i2c_bam {
>  	struct	qup_i2c_tag tag;
>  	struct	dma_chan *dma;
>  	struct	scatterlist *sg;
> +	unsigned int sg_cnt;
>  };
>  
>  struct qup_i2c_dev {
> @@ -195,6 +196,8 @@ struct qup_i2c_dev {
>  	bool			use_dma;
>  	/* The threshold length above which DMA will be used */
>  	unsigned int		dma_threshold;
> +	unsigned int		max_xfer_sg_len;
> +	unsigned int		tag_buf_pos;
>  	struct			dma_pool *dpool;
>  	struct			qup_i2c_tag start_tag;
>  	struct			qup_i2c_bam brx;
> @@ -699,86 +702,86 @@ static int qup_i2c_req_dma(struct qup_i2c_dev *qup)
>  	return 0;
>  }
>  
> -static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
> -			       int num)
> +static int qup_i2c_bam_make_desc(struct qup_i2c_dev *qup, struct i2c_msg *msg)
> +{
> +	int ret = 0, limit = QUP_READ_LIMIT;
> +	u32 len = 0, blocks, rem;
> +	u32 i = 0, tlen, tx_len = 0;
> +	u8 *tags;
> +
> +	qup_i2c_set_blk_data(qup, msg);
> +
> +	blocks = qup->blk.count;
> +	rem = msg->len - (blocks - 1) * limit;
> +
> +	if (msg->flags & I2C_M_RD) {
> +		while (qup->blk.pos < blocks) {
> +			tlen = (i == (blocks - 1)) ? rem : limit;
> +			tags = &qup->start_tag.start[qup->tag_buf_pos + len];
> +			len += qup_i2c_set_tags(tags, qup, msg);
> +			qup->blk.data_len -= tlen;
> +
> +			/* scratch buf to read the start and len tags */
> +			ret = qup_sg_set_buf(&qup->brx.sg[qup->brx.sg_cnt++],
> +					     &qup->brx.tag.start[0],
> +					     2, qup, DMA_FROM_DEVICE);
> +
> +			if (ret)
> +				return ret;
> +
> +			ret = qup_sg_set_buf(&qup->brx.sg[qup->brx.sg_cnt++],
> +					     &msg->buf[limit * i],
> +					     tlen, qup,
> +					     DMA_FROM_DEVICE);
> +			if (ret)
> +				return ret;
> +
> +			i++;
> +			qup->blk.pos = i;
> +		}
> +		ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
> +				     &qup->start_tag.start[qup->tag_buf_pos],
> +				     len, qup, DMA_TO_DEVICE);
> +		if (ret)
> +			return ret;
> +
> +		qup->tag_buf_pos += len;
> +	} else {
> +		while (qup->blk.pos < blocks) {
> +			tlen = (i == (blocks - 1)) ? rem : limit;
> +			tags = &qup->start_tag.start[qup->tag_buf_pos + tx_len];
> +			len = qup_i2c_set_tags(tags, qup, msg);
> +			qup->blk.data_len -= tlen;
> +
> +			ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
> +					     tags, len,
> +					     qup, DMA_TO_DEVICE);
> +			if (ret)
> +				return ret;
> +
> +			tx_len += len;
> +			ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
> +					     &msg->buf[limit * i],
> +					     tlen, qup, DMA_TO_DEVICE);
> +			if (ret)
> +				return ret;
> +			i++;
> +			qup->blk.pos = i;
> +		}
> +
> +		qup->tag_buf_pos += tx_len;
> +	}
> +
> +	return 0;
> +}
> +
> +static int qup_i2c_bam_schedule_desc(struct qup_i2c_dev *qup)
>  {
>  	struct dma_async_tx_descriptor *txd, *rxd = NULL;
> -	int ret = 0, idx = 0, limit = QUP_READ_LIMIT;
> +	int ret = 0;
>  	dma_cookie_t cookie_rx, cookie_tx;
> -	u32 len, blocks, rem;
> -	u32 i, tlen, tx_len, tx_buf = 0, rx_buf = 0, off = 0;
> -	u8 *tags;
> -
> -	while (idx < num) {
> -		tx_len = 0, len = 0, i = 0;
> -
> -		qup->is_last = (idx == (num - 1));
> -
> -		qup_i2c_set_blk_data(qup, msg);
> -
> -		blocks = qup->blk.count;
> -		rem = msg->len - (blocks - 1) * limit;
> -
> -		if (msg->flags & I2C_M_RD) {
> -			while (qup->blk.pos < blocks) {
> -				tlen = (i == (blocks - 1)) ? rem : limit;
> -				tags = &qup->start_tag.start[off + len];
> -				len += qup_i2c_set_tags(tags, qup, msg);
> -				qup->blk.data_len -= tlen;
> -
> -				/* scratch buf to read the start and len tags */
> -				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
> -						     &qup->brx.tag.start[0],
> -						     2, qup, DMA_FROM_DEVICE);
> -
> -				if (ret)
> -					return ret;
> -
> -				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
> -						     &msg->buf[limit * i],
> -						     tlen, qup,
> -						     DMA_FROM_DEVICE);
> -				if (ret)
> -					return ret;
> -
> -				i++;
> -				qup->blk.pos = i;
> -			}
> -			ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
> -					     &qup->start_tag.start[off],
> -					     len, qup, DMA_TO_DEVICE);
> -			if (ret)
> -				return ret;
> -
> -			off += len;
> -		} else {
> -			while (qup->blk.pos < blocks) {
> -				tlen = (i == (blocks - 1)) ? rem : limit;
> -				tags = &qup->start_tag.start[off + tx_len];
> -				len = qup_i2c_set_tags(tags, qup, msg);
> -				qup->blk.data_len -= tlen;
> -
> -				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
> -						     tags, len,
> -						     qup, DMA_TO_DEVICE);
> -				if (ret)
> -					return ret;
> -
> -				tx_len += len;
> -				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
> -						     &msg->buf[limit * i],
> -						     tlen, qup, DMA_TO_DEVICE);
> -				if (ret)
> -					return ret;
> -				i++;
> -				qup->blk.pos = i;
> -			}
> -			off += tx_len;
> -
> -		}
> -		idx++;
> -		msg++;
> -	}
> +	u32 len = 0;
> +	u32 tx_buf = qup->btx.sg_cnt, rx_buf = qup->brx.sg_cnt;
>  
>  	/* schedule the EOT and FLUSH I2C tags */
>  	len = 1;
> @@ -878,11 +881,19 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
>  	return ret;
>  }
>  
> +static void qup_i2c_bam_clear_tag_buffers(struct qup_i2c_dev *qup)
> +{
> +	qup->btx.sg_cnt = 0;
> +	qup->brx.sg_cnt = 0;
> +	qup->tag_buf_pos = 0;
> +}
> +
>  static int qup_i2c_bam_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
>  			    int num)
>  {
>  	struct qup_i2c_dev *qup = i2c_get_adapdata(adap);
>  	int ret = 0;
> +	int idx = 0;
>  
>  	enable_irq(qup->irq);
>  	ret = qup_i2c_req_dma(qup);
> @@ -905,9 +916,34 @@ static int qup_i2c_bam_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
>  		goto out;
>  
>  	writel(qup->clk_ctl, qup->base + QUP_I2C_CLK_CTL);
> +	qup_i2c_bam_clear_tag_buffers(qup);
> +
> +	for (idx = 0; idx < num; idx++) {
> +		qup->msg = msg + idx;
> +		qup->is_last = idx == (num - 1);
> +
> +		ret = qup_i2c_bam_make_desc(qup, qup->msg);
> +		if (ret)
> +			break;
> +
> +		/*
> +		 * Make DMA descriptor and schedule the BAM transfer if its
> +		 * already crossed the maximum length. Since the memory for all
> +		 * tags buffers have been taken for 2 maximum possible
> +		 * transfers length so it will never cross the buffer actual
> +		 * length.
> +		 */
> +		if (qup->btx.sg_cnt > qup->max_xfer_sg_len ||
> +		    qup->brx.sg_cnt > qup->max_xfer_sg_len ||
> +		    qup->is_last) {
> +			ret = qup_i2c_bam_schedule_desc(qup);
> +			if (ret)
> +				break;
> +
> +			qup_i2c_bam_clear_tag_buffers(qup);
> +		}
> +	}
>  

  hmm, is this because of only stress tests or was there any device which
  was using i2c for multiple messages exceeding 64k bytes ?

  Infact we are trying to club two separate messages together across 64k
  boundaries. Not sure if its really correct. So either we club all messages
  fully or club only up to the length that would cover the whole message < 64K
  and send the remaining whole messages in next transfer.

Regards,
  Sricharan
 

> -	qup->msg = msg;
> -	ret = qup_i2c_bam_do_xfer(qup, qup->msg, num);
>  out:
>  	disable_irq(qup->irq);
>  
> @@ -1459,7 +1495,8 @@ static int qup_i2c_probe(struct platform_device *pdev)
>  		else if (ret != 0)
>  			goto nodma;
>  
> -		blocks = (MX_BLOCKS << 1) + 1;
> +		qup->max_xfer_sg_len = (MX_BLOCKS << 1);
> +		blocks = 2 * qup->max_xfer_sg_len + 1;
>  		qup->btx.sg = devm_kzalloc(&pdev->dev,
>  					   sizeof(*qup->btx.sg) * blocks,
>  					   GFP_KERNEL);
> @@ -1603,7 +1640,7 @@ static int qup_i2c_probe(struct platform_device *pdev)
>  	one_bit_t = (USEC_PER_SEC / clk_freq) + 1;
>  	qup->one_byte_t = one_bit_t * 9;
>  	qup->xfer_timeout = TOUT_MIN * HZ +
> -			    usecs_to_jiffies(MX_TX_RX_LEN * qup->one_byte_t);
> +		usecs_to_jiffies(2 * MX_TX_RX_LEN * qup->one_byte_t);
>  
>  	dev_dbg(qup->dev, "IN:block:%d, fifo:%d, OUT:block:%d, fifo:%d\n",
>  		qup->in_blk_sz, qup->in_fifo_sz,
>
Abhishek Sahu Feb. 19, 2018, 11:24 a.m. | #2
On 2018-02-16 10:51, Sricharan R wrote:
> Hi Abhishek,
> 
> On 2/3/2018 1:28 PM, Abhishek Sahu wrote:
>> The BAM mode requires buffer for start tag data and tx, rx SG
>> list. Currently, this is being taken for maximum transfer length
>> (65K). But an I2C transfer can have multiple messages and each
>> message can be of this maximum length so the buffer overflow will
>> happen in this case. Since increasing buffer length won’t be
>> feasible since an I2C transfer can contain any number of messages
>> so this patch does following changes to make i2c transfers working
>> for multiple messages case.
>> 
>> 1. Calculate the required buffers for 2 maximum length messages
>>    (65K * 2).
>> 2. Split the descriptor formation and descriptor scheduling.
>>    The idea is to fit as many messages in one DMA transfers for 65K
>>    threshold value (max_xfer_sg_len). Whenever the sg_cnt is
>>    crossing this, then schedule the BAM transfer and subsequent
>>    transfer will again start from zero.

  <snip>

>> +static void qup_i2c_bam_clear_tag_buffers(struct qup_i2c_dev *qup)
>> +{
>> +	qup->btx.sg_cnt = 0;
>> +	qup->brx.sg_cnt = 0;
>> +	qup->tag_buf_pos = 0;
>> +}
>> +
>>  static int qup_i2c_bam_xfer(struct i2c_adapter *adap, struct i2c_msg 
>> *msg,
>>  			    int num)
>>  {
>>  	struct qup_i2c_dev *qup = i2c_get_adapdata(adap);
>>  	int ret = 0;
>> +	int idx = 0;
>> 
>>  	enable_irq(qup->irq);
>>  	ret = qup_i2c_req_dma(qup);
>> @@ -905,9 +916,34 @@ static int qup_i2c_bam_xfer(struct i2c_adapter 
>> *adap, struct i2c_msg *msg,
>>  		goto out;
>> 
>>  	writel(qup->clk_ctl, qup->base + QUP_I2C_CLK_CTL);
>> +	qup_i2c_bam_clear_tag_buffers(qup);
>> +
>> +	for (idx = 0; idx < num; idx++) {
>> +		qup->msg = msg + idx;
>> +		qup->is_last = idx == (num - 1);
>> +
>> +		ret = qup_i2c_bam_make_desc(qup, qup->msg);
>> +		if (ret)
>> +			break;
>> +
>> +		/*
>> +		 * Make DMA descriptor and schedule the BAM transfer if its
>> +		 * already crossed the maximum length. Since the memory for all
>> +		 * tags buffers have been taken for 2 maximum possible
>> +		 * transfers length so it will never cross the buffer actual
>> +		 * length.
>> +		 */
>> +		if (qup->btx.sg_cnt > qup->max_xfer_sg_len ||
>> +		    qup->brx.sg_cnt > qup->max_xfer_sg_len ||
>> +		    qup->is_last) {
>> +			ret = qup_i2c_bam_schedule_desc(qup);
>> +			if (ret)
>> +				break;
>> +
>> +			qup_i2c_bam_clear_tag_buffers(qup);
>> +		}
>> +	}
>> 
> 
>   hmm, is this because of only stress tests or was there any device 
> which
>   was using i2c for multiple messages exceeding 64k bytes ?

  Its mainly part of stress test but we have test slave devices which
  supports the multiple messages exceeding 64k bytes. Also, in I2C EEPROM
  we can send the multiple messages exceeding 64k bytes. It will roll 
over
  to starting address after its capacity.

> 
>   Infact we are trying to club two separate messages together across 
> 64k
>   boundaries. Not sure if its really correct. So either we club all 
> messages
>   fully or club only up to the length that would cover the whole 
> message < 64K
>   and send the remaining whole messages in next transfer.
> 

  The QUP DMA can be used for any transfer length. It supports greater 
than
  64k also in one go. Only restriction is descriptors memory. clubing all
  messages won't be feasible since there is no restriction on the number 
of
  messages due to which we can't determine the required descriptors size.

  whole message < 64K will require more code changes since we need to 
calculate
  the number of required descriptors in advance. Again in descriptor 
formation,
  the number of required descriptors will be calculated and filled. To 
make the
  code less complicated, I have taken the memory for 128K xfer length 
which
  will make the current code working without any major code changes.

  Thanks,
  Abhishek

Patch

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index 6df65ea..ba717bb 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -155,6 +155,7 @@  struct qup_i2c_bam {
 	struct	qup_i2c_tag tag;
 	struct	dma_chan *dma;
 	struct	scatterlist *sg;
+	unsigned int sg_cnt;
 };
 
 struct qup_i2c_dev {
@@ -195,6 +196,8 @@  struct qup_i2c_dev {
 	bool			use_dma;
 	/* The threshold length above which DMA will be used */
 	unsigned int		dma_threshold;
+	unsigned int		max_xfer_sg_len;
+	unsigned int		tag_buf_pos;
 	struct			dma_pool *dpool;
 	struct			qup_i2c_tag start_tag;
 	struct			qup_i2c_bam brx;
@@ -699,86 +702,86 @@  static int qup_i2c_req_dma(struct qup_i2c_dev *qup)
 	return 0;
 }
 
-static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
-			       int num)
+static int qup_i2c_bam_make_desc(struct qup_i2c_dev *qup, struct i2c_msg *msg)
+{
+	int ret = 0, limit = QUP_READ_LIMIT;
+	u32 len = 0, blocks, rem;
+	u32 i = 0, tlen, tx_len = 0;
+	u8 *tags;
+
+	qup_i2c_set_blk_data(qup, msg);
+
+	blocks = qup->blk.count;
+	rem = msg->len - (blocks - 1) * limit;
+
+	if (msg->flags & I2C_M_RD) {
+		while (qup->blk.pos < blocks) {
+			tlen = (i == (blocks - 1)) ? rem : limit;
+			tags = &qup->start_tag.start[qup->tag_buf_pos + len];
+			len += qup_i2c_set_tags(tags, qup, msg);
+			qup->blk.data_len -= tlen;
+
+			/* scratch buf to read the start and len tags */
+			ret = qup_sg_set_buf(&qup->brx.sg[qup->brx.sg_cnt++],
+					     &qup->brx.tag.start[0],
+					     2, qup, DMA_FROM_DEVICE);
+
+			if (ret)
+				return ret;
+
+			ret = qup_sg_set_buf(&qup->brx.sg[qup->brx.sg_cnt++],
+					     &msg->buf[limit * i],
+					     tlen, qup,
+					     DMA_FROM_DEVICE);
+			if (ret)
+				return ret;
+
+			i++;
+			qup->blk.pos = i;
+		}
+		ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
+				     &qup->start_tag.start[qup->tag_buf_pos],
+				     len, qup, DMA_TO_DEVICE);
+		if (ret)
+			return ret;
+
+		qup->tag_buf_pos += len;
+	} else {
+		while (qup->blk.pos < blocks) {
+			tlen = (i == (blocks - 1)) ? rem : limit;
+			tags = &qup->start_tag.start[qup->tag_buf_pos + tx_len];
+			len = qup_i2c_set_tags(tags, qup, msg);
+			qup->blk.data_len -= tlen;
+
+			ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
+					     tags, len,
+					     qup, DMA_TO_DEVICE);
+			if (ret)
+				return ret;
+
+			tx_len += len;
+			ret = qup_sg_set_buf(&qup->btx.sg[qup->btx.sg_cnt++],
+					     &msg->buf[limit * i],
+					     tlen, qup, DMA_TO_DEVICE);
+			if (ret)
+				return ret;
+			i++;
+			qup->blk.pos = i;
+		}
+
+		qup->tag_buf_pos += tx_len;
+	}
+
+	return 0;
+}
+
+static int qup_i2c_bam_schedule_desc(struct qup_i2c_dev *qup)
 {
 	struct dma_async_tx_descriptor *txd, *rxd = NULL;
-	int ret = 0, idx = 0, limit = QUP_READ_LIMIT;
+	int ret = 0;
 	dma_cookie_t cookie_rx, cookie_tx;
-	u32 len, blocks, rem;
-	u32 i, tlen, tx_len, tx_buf = 0, rx_buf = 0, off = 0;
-	u8 *tags;
-
-	while (idx < num) {
-		tx_len = 0, len = 0, i = 0;
-
-		qup->is_last = (idx == (num - 1));
-
-		qup_i2c_set_blk_data(qup, msg);
-
-		blocks = qup->blk.count;
-		rem = msg->len - (blocks - 1) * limit;
-
-		if (msg->flags & I2C_M_RD) {
-			while (qup->blk.pos < blocks) {
-				tlen = (i == (blocks - 1)) ? rem : limit;
-				tags = &qup->start_tag.start[off + len];
-				len += qup_i2c_set_tags(tags, qup, msg);
-				qup->blk.data_len -= tlen;
-
-				/* scratch buf to read the start and len tags */
-				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
-						     &qup->brx.tag.start[0],
-						     2, qup, DMA_FROM_DEVICE);
-
-				if (ret)
-					return ret;
-
-				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
-						     &msg->buf[limit * i],
-						     tlen, qup,
-						     DMA_FROM_DEVICE);
-				if (ret)
-					return ret;
-
-				i++;
-				qup->blk.pos = i;
-			}
-			ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
-					     &qup->start_tag.start[off],
-					     len, qup, DMA_TO_DEVICE);
-			if (ret)
-				return ret;
-
-			off += len;
-		} else {
-			while (qup->blk.pos < blocks) {
-				tlen = (i == (blocks - 1)) ? rem : limit;
-				tags = &qup->start_tag.start[off + tx_len];
-				len = qup_i2c_set_tags(tags, qup, msg);
-				qup->blk.data_len -= tlen;
-
-				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
-						     tags, len,
-						     qup, DMA_TO_DEVICE);
-				if (ret)
-					return ret;
-
-				tx_len += len;
-				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
-						     &msg->buf[limit * i],
-						     tlen, qup, DMA_TO_DEVICE);
-				if (ret)
-					return ret;
-				i++;
-				qup->blk.pos = i;
-			}
-			off += tx_len;
-
-		}
-		idx++;
-		msg++;
-	}
+	u32 len = 0;
+	u32 tx_buf = qup->btx.sg_cnt, rx_buf = qup->brx.sg_cnt;
 
 	/* schedule the EOT and FLUSH I2C tags */
 	len = 1;
@@ -878,11 +881,19 @@  static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 	return ret;
 }
 
+static void qup_i2c_bam_clear_tag_buffers(struct qup_i2c_dev *qup)
+{
+	qup->btx.sg_cnt = 0;
+	qup->brx.sg_cnt = 0;
+	qup->tag_buf_pos = 0;
+}
+
 static int qup_i2c_bam_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
 			    int num)
 {
 	struct qup_i2c_dev *qup = i2c_get_adapdata(adap);
 	int ret = 0;
+	int idx = 0;
 
 	enable_irq(qup->irq);
 	ret = qup_i2c_req_dma(qup);
@@ -905,9 +916,34 @@  static int qup_i2c_bam_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
 		goto out;
 
 	writel(qup->clk_ctl, qup->base + QUP_I2C_CLK_CTL);
+	qup_i2c_bam_clear_tag_buffers(qup);
+
+	for (idx = 0; idx < num; idx++) {
+		qup->msg = msg + idx;
+		qup->is_last = idx == (num - 1);
+
+		ret = qup_i2c_bam_make_desc(qup, qup->msg);
+		if (ret)
+			break;
+
+		/*
+		 * Make DMA descriptor and schedule the BAM transfer if its
+		 * already crossed the maximum length. Since the memory for all
+		 * tags buffers have been taken for 2 maximum possible
+		 * transfers length so it will never cross the buffer actual
+		 * length.
+		 */
+		if (qup->btx.sg_cnt > qup->max_xfer_sg_len ||
+		    qup->brx.sg_cnt > qup->max_xfer_sg_len ||
+		    qup->is_last) {
+			ret = qup_i2c_bam_schedule_desc(qup);
+			if (ret)
+				break;
+
+			qup_i2c_bam_clear_tag_buffers(qup);
+		}
+	}
 
-	qup->msg = msg;
-	ret = qup_i2c_bam_do_xfer(qup, qup->msg, num);
 out:
 	disable_irq(qup->irq);
 
@@ -1459,7 +1495,8 @@  static int qup_i2c_probe(struct platform_device *pdev)
 		else if (ret != 0)
 			goto nodma;
 
-		blocks = (MX_BLOCKS << 1) + 1;
+		qup->max_xfer_sg_len = (MX_BLOCKS << 1);
+		blocks = 2 * qup->max_xfer_sg_len + 1;
 		qup->btx.sg = devm_kzalloc(&pdev->dev,
 					   sizeof(*qup->btx.sg) * blocks,
 					   GFP_KERNEL);
@@ -1603,7 +1640,7 @@  static int qup_i2c_probe(struct platform_device *pdev)
 	one_bit_t = (USEC_PER_SEC / clk_freq) + 1;
 	qup->one_byte_t = one_bit_t * 9;
 	qup->xfer_timeout = TOUT_MIN * HZ +
-			    usecs_to_jiffies(MX_TX_RX_LEN * qup->one_byte_t);
+		usecs_to_jiffies(2 * MX_TX_RX_LEN * qup->one_byte_t);
 
 	dev_dbg(qup->dev, "IN:block:%d, fifo:%d, OUT:block:%d, fifo:%d\n",
 		qup->in_blk_sz, qup->in_fifo_sz,