From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E366EECE560 for ; Mon, 17 Sep 2018 15:59:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8EA472088F for ; Mon, 17 Sep 2018 15:59:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8EA472088F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=microchip.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728368AbeIQV1m (ORCPT ); Mon, 17 Sep 2018 17:27:42 -0400 Received: from esa3.microchip.iphmx.com ([68.232.153.233]:42046 "EHLO esa3.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726979AbeIQV1l (ORCPT ); Mon, 17 Sep 2018 17:27:41 -0400 X-IronPort-AV: E=Sophos;i="5.53,386,1531810800"; d="scan'208";a="20111628" Received: from smtpout.microchip.com (HELO email.microchip.com) ([198.175.253.82]) by esa3.microchip.iphmx.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 17 Sep 2018 08:59:43 -0700 Received: from [10.159.245.112] (10.10.76.4) by chn-sv-exch02.mchp-main.com (10.10.76.38) with Microsoft SMTP Server id 14.3.352.0; Mon, 17 Sep 2018 08:59:42 -0700 Subject: Re: [PATCH] net: macb: disable scatter-gather for macb on sama5d3 To: David Miller CC: , , , , , , References: <20180914154811.12090-1-nicolas.ferre@microchip.com> <20180917.075813.1145409055019392182.davem@davemloft.net> From: Nicolas Ferre Organization: microchip Message-ID: <8da68995-4019-e0c7-0471-4fdbe40ad52a@microchip.com> Date: Mon, 17 Sep 2018 17:59:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180917.075813.1145409055019392182.davem@davemloft.net> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/09/2018 at 16:58, David Miller wrote: > From: Nicolas Ferre > Date: Fri, 14 Sep 2018 17:48:10 +0200 > >> Create a new configuration for the sama5d3-macb new compatibility string. >> This configuration disables scatter-gather because we experienced lock down >> of the macb interface of this particular SoC under very high load. >> >> Signed-off-by: Nicolas Ferre > > Applied, but are you really sure it isn't just some bug in the driver > or somesuch? Actually, the same IP on other SoCs behaves correctly with same driver. We tried hard to find the root cause of the problem without success and we didn't have confirmation of an issue on Cadence's side either. The symptom is that we have a receive overrun on this interface under heavy load but I think that it is more a result of the issue than the real problem: I cannot escape from this overrun condition: the IP itself is completely blocked. Even if the problem is very difficult to reproduce (simple *perf tools not sufficient), we play safe by simply disabling this feature on this SoC only. Best regards, -- Nicolas Ferre