From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Zolotarov Subject: Re: [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598 Date: Tue, 27 Oct 2015 20:47:48 +0200 Message-ID: <562FC6D4.8000202@cloudius-systems.com> References: <1440085070-13989-1-git-send-email-vladz@cloudius-systems.com> <55DAD1C9.3010802@cloudius-systems.com> <1764015.lv7zT9MUyf@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, jeffrey.t.kirsher@intel.com, jesse.brandeburg@intel.com To: Thomas Monjalon , Konstantin Ananyev , helin.zhang@intel.com Return-path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by dpdk.org (Postfix) with ESMTP id 3331B5A5D for ; Tue, 27 Oct 2015 19:47:50 +0100 (CET) Received: by wicfx6 with SMTP id fx6so172765752wic.1 for ; Tue, 27 Oct 2015 11:47:50 -0700 (PDT) In-Reply-To: <1764015.lv7zT9MUyf@xps13> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 10/27/15 20:09, Thomas Monjalon wrote: > Any Follow-up to this discussion? > Should we mark this patch as rejected? Hmmm... This patch fixes an obvious spec violation. Why would it be rejected? > > 2015-08-24 11:11, Vlad Zolotarov: >> On 08/20/15 18:37, Vlad Zolotarov wrote: >>> According to 82599 and x540 HW specifications RS bit *must* be >>> set in the last descriptor of *every* packet. >>> >>> Before this patch there were 3 types of Tx callbacks that were setting >>> RS bit every tx_rs_thresh descriptors. This patch introduces a set of >>> new callbacks, one for each type mentioned above, that will set the RS >>> bit in every EOP descriptor. >>> >>> ixgbe_set_tx_function() will set the appropriate Tx callback according >>> to the device family. >> [+Jesse and Jeff] >> >> I've started to look at the i40e PMD and it has the same RS bit >> deferring logic >> as ixgbe PMD has (surprise, surprise!.. ;)). To recall, i40e PMD uses a >> descriptor write-back >> completion mode. >> >> From the HW Spec it's unclear if RS bit should be set on *every* descriptor >> with EOP bit. However I noticed that Linux driver, before it moved to >> HEAD write-back mode, was setting RS >> bit on every EOP descriptor. >> >> So, here is a question to Intel guys: could u, pls., clarify this point? >> >> Thanks in advance, >> vlad > >