i2c: xlp9xx: Fix case where SSIF read transaction completes early

[mirror_ubuntu-bionic-kernel.git] / drivers / i2c / busses / i2c-xlp9xx.c

diff --git a/drivers/i2c/busses/i2c-xlp9xx.c b/drivers/i2c/busses/i2c-xlp9xx.c
index f2d224371c08e7ead1e370a2548fa3bbc35f68e3..7c170eba4495cb5689371d0cb0d443ffd014540d 100644 (file)
--- a/drivers/i2c/busses/i2c-xlp9xx.c
+++ b/drivers/i2c/busses/i2c-xlp9xx.c
@@ -188,28 +188,43 @@ 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)