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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6BDF2C433F5 for ; Wed, 22 Sep 2021 11:18:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 566B261107 for ; Wed, 22 Sep 2021 11:18:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235458AbhIVLTd (ORCPT ); Wed, 22 Sep 2021 07:19:33 -0400 Received: from mga18.intel.com ([134.134.136.126]:65341 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230171AbhIVLTc (ORCPT ); Wed, 22 Sep 2021 07:19:32 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="210649436" X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="210649436" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 04:18:00 -0700 X-IronPort-AV: E=Sophos;i="5.85,313,1624345200"; d="scan'208";a="474522094" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 04:17:53 -0700 Received: from andy by smile with local (Exim 4.95-RC2) (envelope-from ) id 1mT0G6-004ANk-OB; Wed, 22 Sep 2021 14:17:50 +0300 Date: Wed, 22 Sep 2021 14:17:50 +0300 From: Andy Shevchenko To: Jonas =?iso-8859-1?Q?Dre=DFler?= Cc: Amitkumar Karwar , Ganapathi Bhat , Xinming Hu , Kalle Valo , "David S. Miller" , Jakub Kicinski , Tsuchiya Yuto , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Maximilian Luz , Bjorn Helgaas , Pali =?iso-8859-1?Q?Roh=E1r?= , Heiner Kallweit , Johannes Berg , Brian Norris , stable@vger.kernel.org Subject: Re: [PATCH v2 1/2] mwifiex: Use non-posted PCI write when setting TX ring write pointer Message-ID: References: <20210914114813.15404-1-verdre@v0yd.nl> <20210914114813.15404-2-verdre@v0yd.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210914114813.15404-2-verdre@v0yd.nl> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Tue, Sep 14, 2021 at 01:48:12PM +0200, Jonas Dreßler wrote: > On the 88W8897 card it's very important the TX ring write pointer is > updated correctly to its new value before setting the TX ready > interrupt, otherwise the firmware appears to crash (probably because > it's trying to DMA-read from the wrong place). The issue is present in > the latest firmware version 15.68.19.p21 of the pcie+usb card. Please, be consistent in the commit message(s) and the code (esp. if the term comes from a specification). Here, PCIe (same in the code, at least that I have noticed, but should be done everywhere). > Since PCI uses "posted writes" when writing to a register, it's not > guaranteed that a write will happen immediately. That means the pointer > might be outdated when setting the TX ready interrupt, leading to > firmware crashes especially when ASPM L1 and L1 substates are enabled > (because of the higher link latency, the write will probably take > longer). > > So fix those firmware crashes by always using a non-posted write for > this specific register write. We do that by simply reading back the > register after writing it, just as a few other PCI drivers do. > > This fixes a bug where during rx/tx traffic and with ASPM L1 substates Ditto. TX/RX. > enabled (the enabled substates are platform dependent), the firmware > crashes and eventually a command timeout appears in the logs. Should it have a Fixes tag? > Cc: stable@vger.kernel.org > Signed-off-by: Jonas Dreßler ... > - /* Write the TX ring write pointer in to reg->tx_wrptr */ > - if (mwifiex_write_reg(adapter, reg->tx_wrptr, > - card->txbd_wrptr | rx_val)) { > + /* Write the TX ring write pointer in to reg->tx_wrptr. > + * The firmware (latest version 15.68.19.p21) of the 88W8897 > + * pcie+usb card seems to crash when getting the TX ready > + * interrupt but the TX ring write pointer points to an outdated > + * address, so it's important we do a non-posted write here to > + * force the completion of the write. > + */ > + if (mwifiex_write_reg_np(adapter, reg->tx_wrptr, > + card->txbd_wrptr | rx_val)) { > mwifiex_dbg(adapter, ERROR, > "SEND DATA: failed to write reg->tx_wrptr\n"); > ret = -1; I'm not sure how this is not a dead code. On top of that, I would rather to call old function and explicitly put the dummy read after it. /* Write the TX ring write pointer in to reg->tx_wrptr */ if (mwifiex_write_reg(adapter, reg->tx_wrptr, card->txbd_wrptr | rx_val)) { ...eliminate dead code in the following patch(es)... } + /* The firmware (latest version 15.68.19.p21) of the 88W8897 + * pcie+usb card seems to crash when getting the TX ready + * interrupt but the TX ring write pointer points to an outdated + * address, so it's important we do a non-posted write here to + * force the completion of the write. + */ mwifiex_read_reg(...); Now, since I found the dummy read function to be present, perhaps you need to dive more into the code and understand why it exists. -- With Best Regards, Andy Shevchenko