MFC r273112: Set the DROP_EN bit before the RX queue is brought up and active.

He noticed issues setting this bit in SRRCTL after the queue was up,
so doing it from the sysctl handler isn't enough and may not actually
work correctly.

This commit doesn't remove the sysctl path or try to change its
behaviour.  I'll talk with others about how to finish fixing that
before I tackle that.

PR:           kern/194311
Submitted by: luigi
MFC after:    3 days
Sponsored by: Norse Corp, Inc

1 files changed, 14 insertions, 0 deletions

diff --git a/sys/dev/ixgbe/ixgbe.c b/sys/dev/ixgbe/ixgbe.c
index e87a496..1d9a1a9 100644
--- a/sys/dev/ixgbe/ixgbe.c
+++ b/sys/dev/ixgbe/ixgbe.c
@@ -4190,6 +4190,20 @@ ixgbe_initialize_receive_units(struct adapter *adapter)
 		srrctl &= ~IXGBE_SRRCTL_BSIZEPKT_MASK;
 		srrctl |= bufsz;
 		srrctl |= IXGBE_SRRCTL_DESCTYPE_ADV_ONEBUF;
+
+		/*
+		 * Set DROP_EN iff we have no flow control and >1 queue.
+		 * Note that srrctl was cleared shortly before during reset,
+		 * so we do not need to clear the bit, but do it just in case
+		 * this code is moved elsewhere.
+		 */
+		if (adapter->num_queues > 1 &&
+		    adapter->hw.fc.requested_mode == ixgbe_fc_none) {
+			srrctl |= IXGBE_SRRCTL_DROP_EN;
+		} else {
+			srrctl &= ~IXGBE_SRRCTL_DROP_EN;
+		}
+
 		IXGBE_WRITE_REG(hw, IXGBE_SRRCTL(i), srrctl);
 
 		/* Setup the HW Rx Head and Tail Descriptor Pointers */