[PATCH v4 1/2] i2c: tegra: Fix PEC support for SMBUS block read

[Akhil R <akhilrajeev@nvidia.com>]

Update the msg->len value correctly for SMBUS block read. The discrepancy
went unnoticed as msg->len is used in SMBUS transfers only when a PEC
byte is added.

Fixes: d7583c8a5748 ("i2c: tegra: Add SMBus block read function")
Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
---
 drivers/i2c/busses/i2c-tegra.c | 38 +++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6aab84c8d22b..83e74b8baf67 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -245,6 +245,7 @@ struct tegra_i2c_hw_feature {
  * @msg_err: error code for completed message
  * @msg_buf: pointer to current message data
  * @msg_buf_remaining: size of unsent data in the message buffer
+ * @msg_len: length of message in current transfer
  * @msg_read: indicates that the transfer is a read access
  * @timings: i2c timings information like bus frequency
  * @multimaster_mode: indicates that I2C controller is in multi-master mode
@@ -279,6 +280,7 @@ struct tegra_i2c_dev {
 	size_t msg_buf_remaining;
 	int msg_err;
 	u8 *msg_buf;
+	__u16 msg_len;
 
 	struct completion dma_complete;
 	struct dma_chan *tx_dma_chan;
@@ -1169,7 +1171,7 @@ static void tegra_i2c_push_packet_header(struct tegra_i2c_dev *i2c_dev,
 	else
 		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
 
-	packet_header = msg->len - 1;
+	packet_header = i2c_dev->msg_len - 1;
 
 	if (i2c_dev->dma_mode && !i2c_dev->msg_read)
 		*dma_buf++ = packet_header;
@@ -1242,20 +1244,32 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 		return err;
 
 	i2c_dev->msg_buf = msg->buf;
+	i2c_dev->msg_len = msg->len;
 
-	/* The condition true implies smbus block read and len is already read */
-	if (msg->flags & I2C_M_RECV_LEN && end_state != MSG_END_CONTINUE)
-		i2c_dev->msg_buf = msg->buf + 1;
-
-	i2c_dev->msg_buf_remaining = msg->len;
 	i2c_dev->msg_err = I2C_ERR_NONE;
 	i2c_dev->msg_read = !!(msg->flags & I2C_M_RD);
 	reinit_completion(&i2c_dev->msg_complete);
 
+	/* *
+	 * For SMBUS block read command, read only 1 byte in the first transfer.
+	 * Adjust that 1 byte for the next transfer in the msg buffer and msg
+	 * length.
+	 */
+	if (msg->flags & I2C_M_RECV_LEN) {
+		if (end_state == MSG_END_CONTINUE) {
+			i2c_dev->msg_len = 1;
+		} else {
+			i2c_dev->msg_buf += 1;
+			i2c_dev->msg_len -= 1;
+		}
+	}
+
+	i2c_dev->msg_buf_remaining = i2c_dev->msg_len;
+
 	if (i2c_dev->msg_read)
-		xfer_size = msg->len;
+		xfer_size = i2c_dev->msg_len;
 	else
-		xfer_size = msg->len + I2C_PACKET_HEADER_SIZE;
+		xfer_size = i2c_dev->msg_len + I2C_PACKET_HEADER_SIZE;
 
 	xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD);
 
@@ -1295,7 +1309,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 	if (!i2c_dev->msg_read) {
 		if (i2c_dev->dma_mode) {
 			memcpy(i2c_dev->dma_buf + I2C_PACKET_HEADER_SIZE,
-			       msg->buf, msg->len);
+			       msg->buf, i2c_dev->msg_len);
 
 			dma_sync_single_for_device(i2c_dev->dma_dev,
 						   i2c_dev->dma_phys,
@@ -1352,7 +1366,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 						i2c_dev->dma_phys,
 						xfer_size, DMA_FROM_DEVICE);
 
-			memcpy(i2c_dev->msg_buf, i2c_dev->dma_buf, msg->len);
+			memcpy(i2c_dev->msg_buf, i2c_dev->dma_buf, i2c_dev->msg_len);
 		}
 	}
 
@@ -1408,8 +1422,8 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], MSG_END_CONTINUE);
 			if (ret)
 				break;
-			/* Set the read byte as msg len */
-			msgs[i].len = msgs[i].buf[0];
+			/* Set the msg length from first byte */
+			msgs[i].len += msgs[i].buf[0];
 			dev_dbg(i2c_dev->dev, "reading %d bytes\n", msgs[i].len);
 		}
 		ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], end_type);
-- 
2.17.1