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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 37B74C8300C for ; Thu, 30 Apr 2020 11:01:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E3C8207DD for ; Thu, 30 Apr 2020 11:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726531AbgD3LBY (ORCPT ); Thu, 30 Apr 2020 07:01:24 -0400 Received: from kernel.crashing.org ([76.164.61.194]:50516 "EHLO kernel.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726413AbgD3LBW (ORCPT ); Thu, 30 Apr 2020 07:01:22 -0400 X-Greylist: delayed 452 seconds by postgrey-1.27 at vger.kernel.org; Thu, 30 Apr 2020 07:01:15 EDT Received: from localhost (gate.crashing.org [63.228.1.57]) (authenticated bits=0) by kernel.crashing.org (8.14.7/8.14.7) with ESMTP id 03UAqvDf025142 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 30 Apr 2020 05:53:01 -0500 Message-ID: <9b5fbaf29adccc5abb66c3d39ecc92a2d5f10d10.camel@kernel.crashing.org> Subject: Re: [PATCH v0 linux master] i2c/busses: Avoid i2c interrupt status clear race condition. From: Benjamin Herrenschmidt To: ryan_chen , Brendan Higgins , Joel Stanley , Andrew Jeffery , linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Thu, 30 Apr 2020 20:52:56 +1000 In-Reply-To: <20200429033737.2781-1-ryan_chen@aspeedtech.com> References: <20200429033737.2781-1-ryan_chen@aspeedtech.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On Wed, 2020-04-29 at 11:37 +0800, ryan_chen wrote: > In AST2600 there have a slow peripheral bus between CPU > and i2c controller. > Therefore GIC i2c interrupt status clear have delay timing, > when CPU issue write clear i2c controller interrupt status. > To avoid this issue, the driver need have read after write > clear at i2c ISR. > > Signed-off-by: ryan_chen Acked-by: Benjamin Herrenschmidt -- > --- > drivers/i2c/busses/i2c-aspeed.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-aspeed.c > b/drivers/i2c/busses/i2c-aspeed.c > index 07c1993274c5..f51702d86a90 100644 > --- a/drivers/i2c/busses/i2c-aspeed.c > +++ b/drivers/i2c/busses/i2c-aspeed.c > @@ -603,6 +603,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, > void *dev_id) > /* Ack all interrupts except for Rx done */ > writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE, > bus->base + ASPEED_I2C_INTR_STS_REG); > + readl(bus->base + ASPEED_I2C_INTR_STS_REG); > irq_remaining = irq_received; > > #if IS_ENABLED(CONFIG_I2C_SLAVE) > @@ -645,9 +646,11 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, > void *dev_id) > irq_received, irq_handled); > > /* Ack Rx done */ > - if (irq_received & ASPEED_I2CD_INTR_RX_DONE) > + if (irq_received & ASPEED_I2CD_INTR_RX_DONE) { > writel(ASPEED_I2CD_INTR_RX_DONE, > bus->base + ASPEED_I2C_INTR_STS_REG); > + readl(bus->base + ASPEED_I2C_INTR_STS_REG); > + } > spin_unlock(&bus->lock); > return irq_remaining ? IRQ_NONE : IRQ_HANDLED; > }