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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 72972C4646A for ; Tue, 11 Sep 2018 23:58:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 212BF2087F for ; Tue, 11 Sep 2018 23:58:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 212BF2087F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.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 S1728054AbeILFAZ (ORCPT ); Wed, 12 Sep 2018 01:00:25 -0400 Received: from mga09.intel.com ([134.134.136.24]:65090 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726980AbeILFAZ (ORCPT ); Wed, 12 Sep 2018 01:00:25 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Sep 2018 16:58:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,362,1531810800"; d="scan'208";a="82726370" Received: from yoojae-mobl1.amr.corp.intel.com (HELO [10.7.153.143]) ([10.7.153.143]) by orsmga003.jf.intel.com with ESMTP; 11 Sep 2018 16:58:44 -0700 Subject: Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly To: Guenter Roeck , Joel Stanley Cc: linux-aspeed@lists.ozlabs.org, Vernon Mauery , OpenBMC Maillist , Brendan Higgins , Linux Kernel Mailing List , linux-i2c@vger.kernel.org, jarkko.nikula@linux.intel.com, =?UTF-8?Q?C=c3=a9dric_Le_Goater?= , Linux ARM , James Feist References: <20180823225731.19063-1-jae.hyun.yoo@linux.intel.com> <20180911183734.GA21976@roeck-us.net> <1f34fe8c-69ef-5f2d-25dc-d5f6037cc558@linux.intel.com> <20180911204107.GA26017@roeck-us.net> <20180911233302.GA18799@roeck-us.net> From: Jae Hyun Yoo Message-ID: <5698ca34-14c9-8d05-c4e6-5acf85ff9d14@linux.intel.com> Date: Tue, 11 Sep 2018 16:58:44 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180911233302.GA18799@roeck-us.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 9/11/2018 4:33 PM, Guenter Roeck wrote: > Looking into the patch, clearing the interrupt status at the end of an > interrupt handler is always suspicious and tends to result in race > conditions (because additional interrupts may have arrived while handling > the existing interrupts, or because interrupt handling itself may trigger > another interrupt). With that in mind, the following patch fixes the > problem for me. > > Guenter > > --- > > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c > index c258c4d9a4c0..c488e6950b7c 100644 > --- a/drivers/i2c/busses/i2c-aspeed.c > +++ b/drivers/i2c/busses/i2c-aspeed.c > @@ -552,6 +552,8 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id) > > spin_lock(&bus->lock); > irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG); > + /* Ack all interrupt bits. */ > + writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG); > irq_remaining = irq_received; > > #if IS_ENABLED(CONFIG_I2C_SLAVE) > @@ -584,8 +586,6 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id) > "irq handled != irq. expected 0x%08x, but was 0x%08x\n", > irq_received, irq_handled); > > - /* Ack all interrupt bits. */ > - writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG); > spin_unlock(&bus->lock); > return irq_remaining ? IRQ_NONE : IRQ_HANDLED; > } > My intention of putting the code at the end of interrupt handler was, to reduce possibility of combined irq calls which is explained in this patch. But YES, I agree with you. It could make a potential race condition as you pointed out. I tested your code change and checked that it works well. Let me take more sufficient test on real H/W. Will share the test result. Thanks a lot! Jae