svn commit: r271645 - head/sys/dev/e1000

[Adrian Chadd]

Author: adrian
Date: Mon Sep 15 19:53:49 2014
New Revision: 271645
URL: http://svnweb.freebsd.org/changeset/base/271645

Log:
  Set DROP_EN on each RX queue if transmit flow-control is disabled.
  
  This allows the NIC to drop frames on the receive queue and not
  cause the MAC to block on receiving to _any_ queue.
  
  Tested:
  
  igb0 at pci0:5:0:0:        class=0x020000 card=0x152115d9 chip=0x15218086 rev=0x01 hdr=0x00
      vendor     = 'Intel Corporation'
      device     = 'I350 Gigabit Network Connection'
      class      = network
      subclass   = ethernet
  
  Discussed with: Eric Joyner <eric.joyner at intel.com>
  
  MFC after:	1 week
  Sponsored by:	Norse Corp, Inc.

Modified:
  head/sys/dev/e1000/if_igb.c

Modified: head/sys/dev/e1000/if_igb.c
==============================================================================
--- head/sys/dev/e1000/if_igb.c	Mon Sep 15 19:48:27 2014	(r271644)
+++ head/sys/dev/e1000/if_igb.c	Mon Sep 15 19:53:49 2014	(r271645)
@@ -4712,6 +4712,18 @@ igb_initialize_receive_units(struct adap
 		rctl |= E1000_RCTL_SZ_2048;
 	}
 
+	/*
+	 * If TX flow control is disabled and there's >1 queue defined,
+	 * enable DROP.
+	 *
+	 * This drops frames rather than hanging the RX MAC for all queues.
+	 */
+	if ((adapter->num_queues > 1) &&
+	    (adapter->fc == e1000_fc_none ||
+	     adapter->fc == e1000_fc_rx_pause)) {
+		srrctl |= E1000_SRRCTL_DROP_EN;
+	}
+
 	/* Setup the Base and Length of the Rx Descriptor Rings */
 	for (int i = 0; i < adapter->num_queues; i++, rxr++) {
 		u64 bus_addr = rxr->rxdma.dma_paddr;
@@ -6255,6 +6267,7 @@ igb_set_flowcntl(SYSCTL_HANDLER_ARGS)
 
 	adapter->hw.fc.current_mode = adapter->hw.fc.requested_mode;
 	e1000_force_mac_fc(&adapter->hw);
+	/* XXX TODO: update DROP_EN on each RX queue if appropriate */
 	return (error);
 }