Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750949AbdHRFul (ORCPT ); Fri, 18 Aug 2017 01:50:41 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:4062 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750709AbdHRFuk (ORCPT ); Fri, 18 Aug 2017 01:50:40 -0400 Subject: Re: [PATCH net v2 2/2] net: ixgbe: Use new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag To: "Tantilov, Emil S" , "davem@davemloft.net" , "Kirsher, Jeffrey T" , "keescook@chromium.org" , "linux-kernel@vger.kernel.org" , "sparclinux@vger.kernel.org" , "intel-wired-lan@lists.osuosl.org" , "alexander.duyck@gmail.com" , "netdev@vger.kernel.org" , "linuxarm@huawei.com" References: <1502940316-13384-1-git-send-email-dingtianhong@huawei.com> <1502940316-13384-3-git-send-email-dingtianhong@huawei.com> <87618083B2453E4A8714035B62D67992B4094F7A@FMSMSX105.amr.corp.intel.com> <2a7fc27b-c2f4-a7a1-9318-3a93531e7670@huawei.com> <87618083B2453E4A8714035B62D67992B4095363@FMSMSX105.amr.corp.intel.com> From: Ding Tianhong Message-ID: Date: Fri, 18 Aug 2017 13:50:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <87618083B2453E4A8714035B62D67992B4095363@FMSMSX105.amr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.23.32] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.59968024.011F,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 7f0d490fbc8621c5784fd2085339ebde Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2272 Lines: 64 On 2017/8/18 13:04, Tantilov, Emil S wrote: >> -----Original Message----- >> From: Ding Tianhong [mailto:dingtianhong@huawei.com] >> Sent: Thursday, August 17, 2017 5:39 PM >> To: Tantilov, Emil S ; davem@davemloft.net; >> Kirsher, Jeffrey T ; keescook@chromium.org; >> linux-kernel@vger.kernel.org; sparclinux@vger.kernel.org; intel-wired- >> lan@lists.osuosl.org; alexander.duyck@gmail.com; netdev@vger.kernel.org; >> linuxarm@huawei.com >> Subject: Re: [PATCH net v2 2/2] net: ixgbe: Use new >> PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag >> >> >> >> On 2017/8/17 22:17, Tantilov, Emil S wrote: >> >>>> ret_val = ixgbe_start_hw_generic(hw); >>>> >>>> -#ifndef CONFIG_SPARC >>>> - /* Disable relaxed ordering */ >>>> - for (i = 0; ((i < hw->mac.max_tx_queues) && >>>> - (i < IXGBE_DCA_MAX_QUEUES_82598)); i++) { >>>> - regval = IXGBE_READ_REG(hw, IXGBE_DCA_TXCTRL(i)); >>>> - regval &= ~IXGBE_DCA_TXCTRL_DESC_WRO_EN; >>>> - IXGBE_WRITE_REG(hw, IXGBE_DCA_TXCTRL(i), regval); >>>> - } >>>> + if (!pcie_relaxed_ordering_enabled(adapter->pdev)) { >>> >>> As Alex mentioned there is no need for this check in any form. >>> >>> The HW defaults to Relaxed Ordering enabled unless it is disabled in >>> the PCIe Device Control Register. So the above logic is already done by >> HW. >>> >>> All you have to do is strip the code disabling relaxed ordering. >>> >> >> Hi Tantilov: >> >> I misunderstood Alex's suggestion, But I still couldn't find the logic >> where >> the HW disable the Relaxed Ordering when the PCIe Device Control Register >> disable it, can you point it out? > > If you look at the datasheet (82599) - the description of CTRL_EXT.RO_DIS (bit 17, 0b): > > Relaxed Ordering Disable. When set to 1b, the device does not request any relaxed > ordering transactions. When this bit is cleared and the Enable Relaxed Ordering bit in > the Device Control register is set, the device requests relaxed ordering transactions per queues as configured in the DCA_RXCTRL[n] and DCA_TXCTRL[n] registers. > > So if you remove the code that clears the bits in DCA_T/RXCTRL relaxed ordering should > be enabled by HW when the bus allows it. > Great, Thanks for your explanation. > Thanks, > Emil > > > . >