net: alx: Work around the DMA RX overflow issue

[ Upstream commit 881d0327db37ad917a367c77aff1afa1ee41e0a9 ]

Note: This is a verified backported patch for stable 4.4 kernel, and it
could also be applied to 4.3/4.2/4.1/3.18/3.16

There is a problem with alx devices, that the network link will be
lost in 1-5 minutes after the device is up.

>From debugging without datasheet, we found the error always
happen when the DMA RX address is set to 0x....fc0, which is very
likely to be a HW/silicon problem.

This patch will apply rx skb with 64 bytes longer space, and if the
allocated skb has a 0x...fc0 address, it will use skb_resever(skb, 64)
to advance the address, so that the RX overflow can be avoided.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=70761
Signed-off-by: Feng Tang <feng.tang@intel.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Tested-by: Ole Lukoie <olelukoie@mail.ru>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
index 754ac8ef2484b55b54aa31da7766acd5104b553e..4736df41f0625037191756c48a39a86244a5c7e3 100644 (file)
--- a/drivers/net/ethernet/atheros/alx/main.c
+++ b/drivers/net/ethernet/atheros/alx/main.c
@@ -86,9 +86,14 @@ static int alx_refill_rx_ring(struct alx_priv *alx, gfp_t gfp)
        while (!cur_buf->skb && next != rxq->read_idx) {
                struct alx_rfd *rfd = &rxq->rfd[cur];
 
-               skb = __netdev_alloc_skb(alx->dev, alx->rxbuf_size, gfp);
+               skb = __netdev_alloc_skb(alx->dev, alx->rxbuf_size + 64, gfp);
                if (!skb)
                        break;
+
+               /* Workround for the HW RX DMA overflow issue */
+               if (((unsigned long)skb->data & 0xfff) == 0xfc0)
+                       skb_reserve(skb, 64);
+
                dma = dma_map_single(&alx->hw.pdev->dev,
                                     skb->data, alx->rxbuf_size,
                                     DMA_FROM_DEVICE);