mv643xx_eth: enforce multiple-of-8-bytes receive buffer size restriction

The mv643xx_eth hardware ignores the lower three bits of the buffer
size field in receive descriptors, causing the reception of full-sized
packets to fail at some MTUs.  Fix this by rounding the size of
allocated receive buffers up to a multiple of eight bytes.

While we are at it, add a bit of extra space to each receive buffer so
that we can handle multiple vlan tags on ingress.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
index e33dfc0165f6..a02a5f4a0294 100644
--- a/drivers/net/mv643xx_eth.c
+++ b/drivers/net/mv643xx_eth.c
@@ -474,11 +474,19 @@ static void rxq_refill(struct rx_queue *rxq)
                 /*
                  * Reserve 2+14 bytes for an ethernet header (the
                  * hardware automatically prepends 2 bytes of dummy
-                 * data to each received packet), 4 bytes for a VLAN
-                 * header, and 4 bytes for the trailing FCS -- 24
-                 * bytes total.
+                 * data to each received packet), 16 bytes for up to
+                 * four VLAN tags, and 4 bytes for the trailing FCS
+                 * -- 36 bytes total.
                  */
-                skb_size = mp->dev->mtu + 24;
+                skb_size = mp->dev->mtu + 36;
+
+                /*
+                 * Make sure that the skb size is a multiple of 8
+                 * bytes, as the lower three bits of the receive
+                 * descriptor's buffer size field are ignored by
+                 * the hardware.
+                 */
+                skb_size = (skb_size + 7) & ~7;
 
                 skb = dev_alloc_skb(skb_size + dma_get_cache_alignment() - 1);
                 if (skb == NULL)
@@ -552,7 +560,7 @@ static int rxq_process(struct rx_queue *rxq, int budget)
                 spin_unlock_irqrestore(&mp->lock, flags);
 
                 dma_unmap_single(NULL, rx_desc->buf_ptr + 2,
-                                 mp->dev->mtu + 24, DMA_FROM_DEVICE);
+                                 rx_desc->buf_size, DMA_FROM_DEVICE);
                 rxq->rx_desc_count--;
                 rx++;