amd-xgbe: Use wmb before updating current descriptor count

The code currently uses the lightweight dma_wmb barrier before updating
the current descriptor count. Under heavy load, the Tx cleanup routine
was seeing the updated current descriptor count before the updated
descriptor information. As a result, the Tx descriptor was being cleaned
up before it was used because it was not "owned" by the hardware yet,
resulting in a Tx queue hang.

Using the wmb barrier insures that the descriptor is updated before the
descriptor counter preventing the Tx queue hang. For extra insurance,
the Tx cleanup routine is changed to grab the current decriptor count on
entry and uses that initial value in the processing loop rather than
trying to chase the current value.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
index a4473d8ff4fa0e1ec7bbdb511f9edd51f1871d71..e9ab8b9f3b9cb8835f7df479a75f9e94666d608b 100644 (file)
--- a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
@@ -1595,7 +1595,7 @@ static void xgbe_dev_xmit(struct xgbe_channel *channel)
                                  packet->rdesc_count, 1);
 
        /* Make sure ownership is written to the descriptor */
-       dma_wmb();
+       wmb();
 
        ring->cur = cur_index + 1;
        if (!packet->skb->xmit_more ||

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
index aae9d5ecd1822b16a2812de3bee503f59113adaa..d2b77d985441f2b1e82889db57eaca6ae133cc55 100644 (file)
--- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
@@ -1807,6 +1807,7 @@ static int xgbe_tx_poll(struct xgbe_channel *channel)
        struct netdev_queue *txq;
        int processed = 0;
        unsigned int tx_packets = 0, tx_bytes = 0;
+       unsigned int cur;
 
        DBGPR("-->xgbe_tx_poll\n");
 
@@ -1814,10 +1815,11 @@ static int xgbe_tx_poll(struct xgbe_channel *channel)
        if (!ring)
                return 0;
 
+       cur = ring->cur;
        txq = netdev_get_tx_queue(netdev, channel->queue_index);
 
        while ((processed < XGBE_TX_DESC_MAX_PROC) &&
-              (ring->dirty != ring->cur)) {
+              (ring->dirty != cur)) {
                rdata = XGBE_GET_DESC_DATA(ring, ring->dirty);
                rdesc = rdata->rdesc;