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ixgbe: Fix issues with SR-IOV loopback when flow control is disabled
This patch allows us to avoid a Tx hang when SR-IOV is enabled. This hang can be triggered by sending small packets at a rate that was triggering Rx missed errors from the adapter while the internal Tx switch and at least one VF are enabled. This was all due to the fact that under heavy stress the Rx FIFO never drained below the flow control high water mark. This resulted in the Tx FIFO being head of line blocked due to the fact that it relies on the flow control high water mark to determine when it is acceptable for the Tx to place a packet in the Rx FIFO. The resolution for this is to set the FCRTH value to the RXPBSIZE - 32 so that even if the ring is almost completely full we can still place Tx packets on the Rx ring and drop incoming Rx traffic if we do not have sufficient space available in the Rx FIFO. Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Tested-by: Sibai Li <sibai.li@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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1 changed files with 8 additions and 1 deletions
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@ -2011,13 +2011,20 @@ s32 ixgbe_fc_enable_generic(struct ixgbe_hw *hw, s32 packetbuf_num)
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IXGBE_WRITE_REG(hw, IXGBE_MFLCN, mflcn_reg);
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IXGBE_WRITE_REG(hw, IXGBE_FCCFG, fccfg_reg);
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fcrth = hw->fc.high_water[packetbuf_num] << 10;
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fcrtl = hw->fc.low_water << 10;
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if (hw->fc.current_mode & ixgbe_fc_tx_pause) {
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fcrth = hw->fc.high_water[packetbuf_num] << 10;
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fcrth |= IXGBE_FCRTH_FCEN;
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if (hw->fc.send_xon)
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fcrtl |= IXGBE_FCRTL_XONE;
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} else {
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/*
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* If Tx flow control is disabled, set our high water mark
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* to Rx FIFO size minus 32 in order prevent Tx switch
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* loopback from stalling on DMA.
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*/
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fcrth = IXGBE_READ_REG(hw, IXGBE_RXPBSIZE(packetbuf_num)) - 32;
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}
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IXGBE_WRITE_REG(hw, IXGBE_FCRTH_82599(packetbuf_num), fcrth);
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