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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 4244FC433DB for ; Thu, 28 Jan 2021 14:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5F3564D9D for ; Thu, 28 Jan 2021 14:14:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231222AbhA1OOa (ORCPT ); Thu, 28 Jan 2021 09:14:30 -0500 Received: from mga05.intel.com ([192.55.52.43]:64119 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231160AbhA1OO1 (ORCPT ); Thu, 28 Jan 2021 09:14:27 -0500 IronPort-SDR: YuAE+pQmA0Q05L345qsGL0IpuuL4d8sNaJVogEGXTFYkwz4ORO/ZmGSPfzzIb1Pw/aG+6d1U3j m+Mw0Zuv276A== X-IronPort-AV: E=McAfee;i="6000,8403,9877"; a="265070140" X-IronPort-AV: E=Sophos;i="5.79,382,1602572400"; d="scan'208";a="265070140" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2021 06:12:41 -0800 IronPort-SDR: SBOYILtEwBDz2zoAPH1EhIlSMU9vgwA85A7VPp0UJZdPwTOk47MkUajuyTh2zgssCzBNM1yg9Y 76v/+aptn/Mw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,382,1602572400"; d="scan'208";a="354185391" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.170]) ([10.237.72.170]) by orsmga003.jf.intel.com with ESMTP; 28 Jan 2021 06:12:40 -0800 Subject: Re: USB2 / USB3 compatibility problems: xhci_hcd 0000:00:06.0: WARN Wrong bounce buffer write length: 0 != 512 To: Andreas Hartmann , linux-usb@vger.kernel.org References: <3b4e35d2-9508-e0aa-eaf8-32e524ad81c4@01019freenet.de> <756e7b88-1142-4758-b8f7-a8eaf510b422@01019freenet.de> <7e953b15-925a-1512-4d15-c07fc03f9059@01019freenet.de> <8de6ecb9-4a39-5742-a358-d6965feffc79@linux.intel.com> <021e1727-0e2e-0207-ace2-4382489eea1f@linux.intel.com> <9c3c9dd7-bcfb-785c-8c11-39f78a7fca01@01019freenet.de> From: Mathias Nyman Autocrypt: addr=mathias.nyman@linux.intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <9c3c9dd7-bcfb-785c-8c11-39f78a7fca01@01019freenet.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org >> If I'm understanding it correctly, you're always creating a bounce >> buffer though it is not necessary (at least in my case - my test patch >> proofed, that no changes at all are necessary). Why aren't you checking >> for URB_NO_TRANSFER_DMA_MAP at the very beginning? Or is it your purpose >> to first basically test your new code path? That would be ok. Bounce buffer is only used when there is no other way of meeting the xHCI alignment requirements. Worst case is once every 255 TRB, and for maximum 1024bytes. Each TRB can point to 64K of data. I can't go against the spec just because it doesn't cause issues in your two usecases. The overhead of the bounce buffer usage is so small there's no point in that kind of optimization. URB_NO_TRANSFER_DMA_MAP only indicates the data was DMA mapped before driver submitted the URB, so usb core does not need to map it. I was speculating that it could be a cause why data is so oddly aligned (urbs with data starting at less than 512 bytes from 64k boundary), and thus not meeting the xHC boundary and aligment requirements even if data is otherwise contiguous. xHC controller doesn't care who mapped the data, or if data is in a sg list or already contiguous in urb->transfer_buffer as long as we follow the aligment and boudary rules. Bug was that driver assumed the data that needed to be bounce buffered was in a sg list. Your cased proved it could be in urb->tranfer_buffer instead. >> >> I tested with the notebook (in both directions) - it seems to work - I >> didn't get any problems though I used 24 kB bulk packets. Throughput was >> unaltered high. >> >> I'm doing the same test tomorrow with the other USB 3.1 controller! > > Successfully tested on the other USB 3.1 host. > Thank you, much appreciated. I think I'll submit this patch as it is (with a proper commit message) can I add reported-by: Andreas Hartmann , and tested-by: Andreas Hartmann tags to the patch? -Mathias