From patchwork Tue Aug 7 08:04:17 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Waskiewicz Jr, Peter P" X-Patchwork-Id: 175517 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 06DB92C0081 for ; Tue, 7 Aug 2012 18:05:56 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752495Ab2HGIFu (ORCPT ); Tue, 7 Aug 2012 04:05:50 -0400 Received: from mga03.intel.com ([143.182.124.21]:49719 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752007Ab2HGIFr (ORCPT ); Tue, 7 Aug 2012 04:05:47 -0400 Received: from azsmga001.ch.intel.com ([10.2.17.19]) by azsmga101.ch.intel.com with ESMTP; 07 Aug 2012 01:05:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="177804853" Received: from unknown (HELO ppwaskie-mobl2.amr.corp.intel.com) ([10.255.12.160]) by azsmga001.ch.intel.com with ESMTP; 07 Aug 2012 01:05:46 -0700 From: Peter P Waskiewicz Jr To: davem@davemloft.net Cc: Stefan Assmann , netdev@vger.kernel.org, gospo@redhat.com, sassmann@redhat.com, Peter P Waskiewicz Jr Subject: [net 3/3] igb: add delay to allow igb loopback test to succeed on 8086:10c9 Date: Tue, 7 Aug 2012 01:04:17 -0700 Message-Id: <1344326657-9376-4-git-send-email-peter.p.waskiewicz.jr@intel.com> X-Mailer: git-send-email 1.7.11.2 In-Reply-To: <1344326657-9376-1-git-send-email-peter.p.waskiewicz.jr@intel.com> References: <1344326657-9376-1-git-send-email-peter.p.waskiewicz.jr@intel.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Stefan Assmann Some 8086:10c9 NICs have a problem completing the ethtool loopback test. The result looks like this: ethtool -t eth1 The test result is FAIL The test extra info: Register test (offline) 0 Eeprom test (offline) 0 Interrupt test (offline) 0 Loopback test (offline) 13 Link test (on/offline) 0 A bisect clearly points to commit a95a07445ee97a2fef65befafbadcc30ca1bd145. However that seems to only trigger the bug. While adding some printk the problem disappeared, so this might be a timing issue. After some trial and error I discovered that adding a small delay just before igb_write_phy_reg() in igb_integrated_phy_loopback() allows the loopback test to succeed. I was unable to figure out the root cause so far but I expect it to be somewhere in the following executing path igb_integrated_phy_loopback ->igb_write_phy_reg_igp ->igb_write_phy_reg_mdic ->igb_acquire_phy_82575 ->igb_acquire_swfw_sync_82575 The problem could only be observed on 8086:10c9 NICs so far and not all of them show the behaviour. I did not restrict the workaround to this type of NIC as it should do no harm to other igb NICs. With the patch below the loopback test succeeded 500 times in a row using a NIC that would otherwise fail. Signed-off-by: Stefan Assmann Tested-by: Aaron Brown Signed-off-by: Peter P Waskiewicz Jr --- drivers/net/ethernet/intel/igb/igb_ethtool.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/ethernet/intel/igb/igb_ethtool.c b/drivers/net/ethernet/intel/igb/igb_ethtool.c index 90550f5..7059111 100644 --- a/drivers/net/ethernet/intel/igb/igb_ethtool.c +++ b/drivers/net/ethernet/intel/igb/igb_ethtool.c @@ -1498,6 +1498,9 @@ static int igb_integrated_phy_loopback(struct igb_adapter *adapter) break; } + /* add small delay to avoid loopback test failure */ + msleep(50); + /* force 1000, set loopback */ igb_write_phy_reg(hw, PHY_CONTROL, 0x4140);