2 files changed, 8 insertions, 2 deletions

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index aac22a1e85b8..b14a717ac3e8 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -141,6 +141,8 @@ struct efx_special_buffer {
  * @len: Length of this fragment.
  *      This field is zero when the queue slot is empty.
  * @unmap_len: Length of this fragment to unmap
+ * @dma_offset: Offset of @dma_addr from the address of the backing DMA mapping.
+ * Only valid if @unmap_len != 0.
  */
 struct efx_tx_buffer {
         union {
@@ -154,6 +156,7 @@ struct efx_tx_buffer {
         unsigned short flags;
         unsigned short len;
         unsigned short unmap_len;
+        unsigned short dma_offset;
 };
 #define EFX_TX_BUF_CONT         1       /* not last descriptor of packet */
 #define EFX_TX_BUF_SKB          2       /* buffer is last part of skb */
diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index 282692c48e6b..c49d1fb16965 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -65,8 +65,7 @@ static void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
 {
         if (buffer->unmap_len) {
                 struct device *dma_dev = &tx_queue->efx->pci_dev->dev;
-                dma_addr_t unmap_addr = (buffer->dma_addr + buffer->len -
-                                         buffer->unmap_len);
+                dma_addr_t unmap_addr = buffer->dma_addr - buffer->dma_offset;
                 if (buffer->flags & EFX_TX_BUF_MAP_SINGLE)
                         dma_unmap_single(dma_dev, unmap_addr, buffer->unmap_len,
                                          DMA_TO_DEVICE);
@@ -414,6 +413,7 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
                 /* Transfer ownership of the unmapping to the final buffer */
                 buffer->flags = EFX_TX_BUF_CONT | dma_flags;
                 buffer->unmap_len = unmap_len;
+                buffer->dma_offset = buffer->dma_addr - unmap_addr;
                 unmap_len = 0;
 
                 /* Get address and size of next fragment */
@@ -980,6 +980,7 @@ static int efx_tso_put_header(struct efx_tx_queue *tx_queue,
                         return -ENOMEM;
                 }
                 buffer->unmap_len = buffer->len;
+                buffer->dma_offset = 0;
                 buffer->flags |= EFX_TX_BUF_MAP_SINGLE;
         }
 
@@ -1121,6 +1122,7 @@ static void tso_fill_packet_with_fragment(struct efx_tx_queue *tx_queue,
         if (st->in_len == 0) {
                 /* Transfer ownership of the DMA mapping */
                 buffer->unmap_len = st->unmap_len;
+                buffer->dma_offset = buffer->unmap_len - buffer->len;
                 buffer->flags |= st->dma_flags;
                 st->unmap_len = 0;
         }
@@ -1219,6 +1221,7 @@ static int tso_start_new_packet(struct efx_tx_queue *tx_queue,
                 if (is_last) {
                         buffer->flags = EFX_TX_BUF_CONT | EFX_TX_BUF_MAP_SINGLE;
                         buffer->unmap_len = st->header_unmap_len;
+                        buffer->dma_offset = 0;
                         /* Ensure we only unmap them once in case of a
                          * later DMA mapping error and rollback
                          */