ixgbe: Clear head write-back registers on VF reset

The Tx head write-back registers are not cleared during an FLR or VF reset.
As a result a configuration that had head write-back enabled can leave the
registers set after the driver is unloaded.  If the next driver loaded doesn't
use the write-back registers this can lead to a bad configuration where
head write-back is enabled, but the driver didn't request it.

To avoid this situation the PF should be resetting the Tx head write-back
registers when the VF requests a reset.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
index 43e10c67ac4e..0558c7139f38 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
@@ -698,6 +698,15 @@ static int ixgbe_vf_reset_msg(struct ixgbe_adapter *adapter, u32 vf)
 	reg |= (1 << vf_shift);
 	IXGBE_WRITE_REG(hw, IXGBE_VMECM(reg_offset), reg);
 
+	/*
+	 * Reset the VFs TDWBAL and TDWBAH registers
+	 * which are not cleared by an FLR
+	 */
+	for (i = 0; i < q_per_pool; i++) {
+		IXGBE_WRITE_REG(hw, IXGBE_PVFTDWBAHn(q_per_pool, vf, i), 0);
+		IXGBE_WRITE_REG(hw, IXGBE_PVFTDWBALn(q_per_pool, vf, i), 0);
+	}
+
 	/* reply to reset with ack and vf mac address */
 	msgbuf[0] = IXGBE_VF_RESET;
 	if (!is_zero_ether_addr(vf_mac)) {