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Subject[PATCH 4.9 50/50] net: stmmac: Set dma ring length before enabling the DMA
Date
From: Lars Persson <lars.persson@axis.com>

This was fixed in upstream by commit 7d9e6c5afab6 ("net: stmmac: Integrate
XGMAC into main driver flow") that is a new feature commit.

We found a race condition in the DMA init sequence that hits if the
PHY already has link up during stmmac_hw_setup. Since the ring length
was programmed after enabling the RX path, we might receive a packet
before the correct ring length is programmed. When that happened we
could not get reliable interrupts for DMA RX and the MTL complained
about RX FIFO overrun.

Signed-off-by: Lars Persson <larper@axis.com>
Cc: stable@vger.kernel.org # 4.9.x
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1747,11 +1747,6 @@ static int stmmac_hw_setup(struct net_de
if (ret < 0)
pr_warn("%s: failed debugFS registration\n", __func__);
#endif
- /* Start the ball rolling... */
- pr_debug("%s: DMA RX/TX processes started...\n", dev->name);
- priv->hw->dma->start_tx(priv->ioaddr);
- priv->hw->dma->start_rx(priv->ioaddr);
-
/* Dump DMA/MAC registers */
if (netif_msg_hw(priv)) {
priv->hw->mac->dump_regs(priv->hw);
@@ -1779,6 +1774,11 @@ static int stmmac_hw_setup(struct net_de
if (priv->tso)
priv->hw->dma->enable_tso(priv->ioaddr, 1, STMMAC_CHAN0);

+ /* Start the ball rolling... */
+ pr_debug("%s: DMA RX/TX processes started...\n", dev->name);
+ priv->hw->dma->start_tx(priv->ioaddr);
+ priv->hw->dma->start_rx(priv->ioaddr);
+
return 0;
}


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