net: alx: Work around the DMA RX overflow issue
Commit 26c5f03 uses a new skb allocator to avoid the RFD overflow
issue.
But 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.
So one idea is instead of adding a new allocator, why not just
hitting the right target by avaiding the error-prone DMA address?
This patch will actually
* Remove the commit 26c5f03
* 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.
In theory this method should also apply to atl1c driver, which
I can't find anyone who can help to test on real devices.
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>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
index c98acdc..e708e36 100644
--- a/drivers/net/ethernet/atheros/alx/main.c
+++ b/drivers/net/ethernet/atheros/alx/main.c
@@ -70,35 +70,6 @@
}
}
-static struct sk_buff *alx_alloc_skb(struct alx_priv *alx, gfp_t gfp)
-{
- struct sk_buff *skb;
- struct page *page;
-
- if (alx->rx_frag_size > PAGE_SIZE)
- return __netdev_alloc_skb(alx->dev, alx->rxbuf_size, gfp);
-
- page = alx->rx_page;
- if (!page) {
- alx->rx_page = page = alloc_page(gfp);
- if (unlikely(!page))
- return NULL;
- alx->rx_page_offset = 0;
- }
-
- skb = build_skb(page_address(page) + alx->rx_page_offset,
- alx->rx_frag_size);
- if (likely(skb)) {
- alx->rx_page_offset += alx->rx_frag_size;
- if (alx->rx_page_offset >= PAGE_SIZE)
- alx->rx_page = NULL;
- else
- get_page(page);
- }
- return skb;
-}
-
-
static int alx_refill_rx_ring(struct alx_priv *alx, gfp_t gfp)
{
struct alx_rx_queue *rxq = &alx->rxq;
@@ -115,9 +86,22 @@
while (!cur_buf->skb && next != rxq->read_idx) {
struct alx_rfd *rfd = &rxq->rfd[cur];
- skb = alx_alloc_skb(alx, gfp);
+ /*
+ * When DMA RX address is set to something like
+ * 0x....fc0, it will be very likely to cause DMA
+ * RFD overflow issue.
+ *
+ * To work around it, we apply rx skb with 64 bytes
+ * longer space, and offset the address whenever
+ * 0x....fc0 is detected.
+ */
+ skb = __netdev_alloc_skb(alx->dev, alx->rxbuf_size + 64, gfp);
if (!skb)
break;
+
+ 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);
@@ -153,7 +137,6 @@
alx_write_mem16(&alx->hw, ALX_RFD_PIDX, cur);
}
-
return count;
}
@@ -622,11 +605,6 @@
kfree(alx->txq.bufs);
kfree(alx->rxq.bufs);
- if (alx->rx_page) {
- put_page(alx->rx_page);
- alx->rx_page = NULL;
- }
-
dma_free_coherent(&alx->hw.pdev->dev,
alx->descmem.size,
alx->descmem.virt,
@@ -681,7 +659,6 @@
alx->dev->name, alx);
if (!err)
goto out;
-
/* fall back to legacy interrupt */
pci_disable_msi(alx->hw.pdev);
}
@@ -725,7 +702,6 @@
struct pci_dev *pdev = alx->hw.pdev;
struct alx_hw *hw = &alx->hw;
int err;
- unsigned int head_size;
err = alx_identify_hw(alx);
if (err) {
@@ -741,12 +717,7 @@
hw->smb_timer = 400;
hw->mtu = alx->dev->mtu;
-
alx->rxbuf_size = ALX_MAX_FRAME_LEN(hw->mtu);
- head_size = SKB_DATA_ALIGN(alx->rxbuf_size + NET_SKB_PAD) +
- SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- alx->rx_frag_size = roundup_pow_of_two(head_size);
-
alx->tx_ringsz = 256;
alx->rx_ringsz = 512;
hw->imt = 200;
@@ -848,7 +819,6 @@
{
struct alx_priv *alx = netdev_priv(netdev);
int max_frame = ALX_MAX_FRAME_LEN(mtu);
- unsigned int head_size;
if ((max_frame < ALX_MIN_FRAME_SIZE) ||
(max_frame > ALX_MAX_FRAME_SIZE))
@@ -860,9 +830,6 @@
netdev->mtu = mtu;
alx->hw.mtu = mtu;
alx->rxbuf_size = max(max_frame, ALX_DEF_RXBUF_SIZE);
- head_size = SKB_DATA_ALIGN(alx->rxbuf_size + NET_SKB_PAD) +
- SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- alx->rx_frag_size = roundup_pow_of_two(head_size);
netdev_update_features(netdev);
if (netif_running(netdev))
alx_reinit(alx);