[ 3.5.y.z extended stable ] Patch "igb: Remove artificial restriction on RQDPC stat reading" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Thu Feb 28 11:59:04 UTC 2013

This is a note to let you know that I have just added a patch titled

    igb: Remove artificial restriction on RQDPC stat reading

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From befe9ccdacc8ea6230f51892fec4d8a7c5d335a3 Mon Sep 17 00:00:00 2001
From: Alexander Duyck <alexander.h.duyck at intel.com>
Date: Wed, 8 Aug 2012 05:23:22 +0000
Subject: [PATCH] igb: Remove artificial restriction on RQDPC stat reading

commit ae1c07a6b7ced6c0c94c99e3b53f4e7856fa8bff upstream.

For some reason the reading of the RQDPC register was being artificially
limited to 4K.  Instead of limiting the value we should read the value and
add the full amount.  Otherwise this can lead to a misleading number of
dropped packets when the actual value is in fact much higher.

Signed-off-by: Alexander Duyck <alexander.h.duyck at intel.com>
Tested-by: Jeff Pieper   <jeffrey.e.pieper at intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/net/ethernet/intel/igb/igb_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 64a0f74..9269192 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4580,11 +4580,13 @@ void igb_update_stats(struct igb_adapter *adapter,
 	bytes = 0;
 	packets = 0;
 	for (i = 0; i < adapter->num_rx_queues; i++) {
-		u32 rqdpc_tmp = rd32(E1000_RQDPC(i)) & 0x0FFF;
+		u32 rqdpc = rd32(E1000_RQDPC(i));
 		struct igb_ring *ring = adapter->rx_ring[i];

-		ring->rx_stats.drops += rqdpc_tmp;
-		net_stats->rx_fifo_errors += rqdpc_tmp;
+		if (rqdpc) {
+			ring->rx_stats.drops += rqdpc;
+			net_stats->rx_fifo_errors += rqdpc;
+		}

 		do {
 			start = u64_stats_fetch_begin_bh(&ring->rx_syncp);

More information about the kernel-team mailing list