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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 0B9D7C433F5 for ; Fri, 24 Sep 2021 10:06:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7CFD600D4 for ; Fri, 24 Sep 2021 10:06:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245510AbhIXKIV (ORCPT ); Fri, 24 Sep 2021 06:08:21 -0400 Received: from mga17.intel.com ([192.55.52.151]:29010 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244963AbhIXKIU (ORCPT ); Fri, 24 Sep 2021 06:08:20 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10116"; a="204198561" X-IronPort-AV: E=Sophos;i="5.85,319,1624345200"; d="scan'208";a="204198561" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2021 03:06:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,319,1624345200"; d="scan'208";a="703468211" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.84]) ([10.237.72.84]) by fmsmga006.fm.intel.com with ESMTP; 24 Sep 2021 03:06:35 -0700 Subject: Re: [PATCH v1 2/2] mmc: sdhci: Use the SW timer when the HW timer cannot meet the timeout value required by the device To: Bean Huo , Ulf Hansson Cc: Bean Huo , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210917172727.26834-1-huobean@gmail.com> <20210917172727.26834-3-huobean@gmail.com> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: <93292ef4-8548-d2ba-d803-d3b40b7e6c1d@intel.com> Date: Fri, 24 Sep 2021 13:07:14 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/09/21 12:17 pm, Bean Huo wrote: > On Fri, 2021-09-24 at 08:29 +0300, Adrian Hunter wrote: >>> If the data transmission timeout value required by the device >>> exceeds >>> the maximum timeout value of the host HW timer, we still use the HW >>> timer with the maximum timeout value of the HW timer. This setting >>> is >>> suitable for most R/W situations. But sometimes, the device will >>> complete >>> the R/W task within its required timeout value (greater than the HW >>> timer). >>> In this case, the HW timer for data transmission will time out. >>> Currently, in this condition, we disable the HW timer and use the >>> SW >>> timer only when the SDHCI_QUIRK2_DISABLE_HW_TIMEOUT quirk is set by >>> the >>> host driver. The patch is to remove this if statement restriction >>> and >>> allow data transmission to use the SW timer when the hardware timer >>> cannot >>> meet the required timeout value. >> >> >> The reason it is a quirk is because it does not work for all >> hardware. >> >> For some controllers the timeout cannot really be disabled, only the >> >> interrupt is disabled, and then the controller never indicates >> completion >> >> if the timeout is exceeded. > > Hi Adrian, > Thanks for your review. > > Yes, you are right. But this quirk prevents disabling the hardware timeoutIRQ. The purpose of this patch is to disable the hardware timeout IRQ and > select the software timeout. > > void __sdhci_set_timeout(struct sdhci_host *host, struct mmc_command > *cmd) > { > bool too_big = false; > u8 count = sdhci_calc_timeout(host, cmd, &too_big); > > if (too_big) { > sdhci_calc_sw_timeout(host, cmd); > sdhci_set_data_timeout_irq(host, false); // disable IRQ > } else if (!(host->ier & SDHCI_INT_DATA_TIMEOUT)) { > sdhci_set_data_timeout_irq(host, true); > } > > sdhci_writeb(host, count, SDHCI_TIMEOUT_CONTROL); > } > > > The driver has detected that the hardware timer cannot meet the timeout > requirements of the device, but we still use the hardware timer, which will > allow potential timeout issuea . Rather than allowing a potential > problem to exist, why can’t software timing be used to avoid this > problem? Timeouts aren't that accurate. The maximum is assumed still to work. mmc->max_busy_timeout is used to tell the core what the maximum is.