releases/4.9.170/net-stmmac-set-dma-ring-length-before-enabling-the-dma.patch

   1 From lars.persson@axis.com  Wed Apr 17 22:13:01 2019
   2 From: Lars Persson <lars.persson@axis.com>
   3 Date: Mon, 15 Apr 2019 09:50:34 +0200
   4 Subject: net: stmmac: Set dma ring length before enabling the DMA
   5 To: stable@vger.kernel.org
   6 Cc: peppe.cavallaro@st.com, alexandre.torgue@st.com, joabreu@synopsys.com, Lars Persson <larper@axis.com>
   7 Message-ID: <20190415075034.6236-1-larper@axis.com>
   8
   9 From: Lars Persson <lars.persson@axis.com>
  10
  11 This was fixed in upstream by commit 7d9e6c5afab6 ("net: stmmac: Integrate
  12 XGMAC into main driver flow") that is a new feature commit.
  13
  14 We found a race condition in the DMA init sequence that hits if the
  15 PHY already has link up during stmmac_hw_setup. Since the ring length
  16 was programmed after enabling the RX path, we might receive a packet
  17 before the correct ring length is programmed. When that happened we
  18 could not get reliable interrupts for DMA RX and the MTL complained
  19 about RX FIFO overrun.
  20
  21 Signed-off-by: Lars Persson <larper@axis.com>
  22 Cc: stable@vger.kernel.org # 4.9.x
  23 Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
  24 Cc: Alexandre Torgue <alexandre.torgue@st.com>
  25 Cc: Jose Abreu <joabreu@synopsys.com>
  26 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  27
  28 ---
  29  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   10 +++++-----
  30  1 file changed, 5 insertions(+), 5 deletions(-)
  31
  32 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
  33 +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
  34 @@ -1747,11 +1747,6 @@ static int stmmac_hw_setup(struct net_de
  35         if (ret < 0)
  36                 pr_warn("%s: failed debugFS registration\n", __func__);
  37  #endif
  38 -       /* Start the ball rolling... */
  39 -       pr_debug("%s: DMA RX/TX processes started...\n", dev->name);
  40 -       priv->hw->dma->start_tx(priv->ioaddr);
  41 -       priv->hw->dma->start_rx(priv->ioaddr);
  42 -
  43         /* Dump DMA/MAC registers */
  44         if (netif_msg_hw(priv)) {
  45                 priv->hw->mac->dump_regs(priv->hw);
  46 @@ -1779,6 +1774,11 @@ static int stmmac_hw_setup(struct net_de
  47         if (priv->tso)
  48                 priv->hw->dma->enable_tso(priv->ioaddr, 1, STMMAC_CHAN0);
  49
  50 +       /* Start the ball rolling... */
  51 +       pr_debug("%s: DMA RX/TX processes started...\n", dev->name);
  52 +       priv->hw->dma->start_tx(priv->ioaddr);
  53 +       priv->hw->dma->start_rx(priv->ioaddr);
  54 +
  55         return 0;
  56  }
  57