Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux

Pull i2c fix from Wolfram Sang:
 "A single driver bugfix for I2C.

  The bug was found by systematically stress testing the driver, so I am
  confident to merge it that late in the cycle although it is probably
  unusually large"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: xlp9xx: Fix case where SSIF read transaction completes early

1 files changed, 28 insertions, 13 deletions

diff --git a/drivers/i2c/busses/i2c-xlp9xx.c b/drivers/i2c/busses/i2c-xlp9xx.c
index 1f41a4f89c08f4..8a873975cf1252 100644
--- a/drivers/i2c/busses/i2c-xlp9xx.c
+++ b/drivers/i2c/busses/i2c-xlp9xx.c
@@ -191,28 +191,43 @@ static void xlp9xx_i2c_drain_rx_fifo(struct xlp9xx_i2c_dev *priv)
 	if (priv->len_recv) {
 		/* read length byte */
 		rlen = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_MRXFIFO);
+
+		/*
+		 * We expect at least 2 interrupts for I2C_M_RECV_LEN
+		 * transactions. The length is updated during the first
+		 * interrupt, and the buffer contents are only copied
+		 * during subsequent interrupts. If in case the interrupts
+		 * get merged we would complete the transaction without
+		 * copying out the bytes from RX fifo. To avoid this now we
+		 * drain the fifo as and when data is available.
+		 * We drained the rlen byte already, decrement total length
+		 * by one.
+		 */
+
+		len--;
 		if (rlen > I2C_SMBUS_BLOCK_MAX || rlen == 0) {
 			rlen = 0;	/*abort transfer */
 			priv->msg_buf_remaining = 0;
 			priv->msg_len = 0;
-		} else {
-			*buf++ = rlen;
-			if (priv->client_pec)
-				++rlen; /* account for error check byte */
-			/* update remaining bytes and message length */
-			priv->msg_buf_remaining = rlen;
-			priv->msg_len = rlen + 1;
+			xlp9xx_i2c_update_rlen(priv);
+			return;
 		}
+
+		*buf++ = rlen;
+		if (priv->client_pec)
+			++rlen; /* account for error check byte */
+		/* update remaining bytes and message length */
+		priv->msg_buf_remaining = rlen;
+		priv->msg_len = rlen + 1;
 		xlp9xx_i2c_update_rlen(priv);
 		priv->len_recv = false;
-	} else {
-		len = min(priv->msg_buf_remaining, len);
-		for (i = 0; i < len; i++, buf++)
-			*buf = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_MRXFIFO);
-
-		priv->msg_buf_remaining -= len;
 	}
 
+	len = min(priv->msg_buf_remaining, len);
+	for (i = 0; i < len; i++, buf++)
+		*buf = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_MRXFIFO);
+
+	priv->msg_buf_remaining -= len;
 	priv->msg_buf = buf;
 
 	if (priv->msg_buf_remaining)