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=-8.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C3645C433E2 for ; Tue, 21 Jul 2020 10:49:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A172120674 for ; Tue, 21 Jul 2020 10:49:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="W6ArY2zY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729370AbgGUKtG (ORCPT ); Tue, 21 Jul 2020 06:49:06 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:35733 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727043AbgGUKtG (ORCPT ); Tue, 21 Jul 2020 06:49:06 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1595328545; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=hWSCkjwa6XTH8wbP9rLLbwZRQrSZSARhWd3jpGdV9Qs=; b=W6ArY2zY9uBILB+tpU3OXMgh4efGvksJKrcU47Dctn9epu3ErP9795X/ETcXTS3FvVTRK0qk kxBnvhJ0/T/3r2zgNHwNBjZtX0gy3dAMm88QvAynAF5nkVa6bIVxSBiHbODFbATWkMA15APl 9CeEY3OpuKdjX549Vfnoat1trmM= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n16.prod.us-east-1.postgun.com with SMTP id 5f16c805427cd557667500df (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 21 Jul 2020 10:48:37 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 42CD6C433A0; Tue, 21 Jul 2020 10:48:36 +0000 (UTC) Received: from [192.168.43.98] (unknown [157.48.50.75]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: akashast) by smtp.codeaurora.org (Postfix) with ESMTPSA id 20993C433CA; Tue, 21 Jul 2020 10:48:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 20993C433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=akashast@codeaurora.org Subject: Re: [PATCH] i2c: i2c-qcom-geni: Fix DMA transfer race To: Douglas Anderson , Wolfram Sang Cc: Sai Prakash Ranjan , Rajendra Nayak , swboyd@chromium.org, Alok Chauhan , Andy Gross , Bjorn Andersson , Girish Mahadevan , Karthikeyan Ramasubramanian , Wolfram Sang , linux-arm-msm@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200720172448.1.I7efdf6efaa6edadbb690196cd4fbe3392a582c89@changeid> From: Akash Asthana Message-ID: Date: Tue, 21 Jul 2020 16:18:23 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200720172448.1.I7efdf6efaa6edadbb690196cd4fbe3392a582c89@changeid> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/21/2020 5:54 AM, Douglas Anderson wrote: > When I have KASAN enabled on my kernel and I start stressing the > touchscreen my system tends to hang. The touchscreen is one of the > only things that does a lot of big i2c transfers and ends up hitting > the DMA paths in the geni i2c driver. It appears that KASAN adds > enough delay in my system to tickle a race condition in the DMA setup > code. > > When the system hangs, I found that it was running the geni_i2c_irq() > over and over again. It had these: > > m_stat = 0x04000080 > rx_st = 0x30000011 > dm_tx_st = 0x00000000 > dm_rx_st = 0x00000000 > dma = 0x00000001 > > Notably we're in DMA mode but are getting M_RX_IRQ_EN and > M_RX_FIFO_WATERMARK_EN over and over again. > > Putting some traces in geni_i2c_rx_one_msg() showed that when we > failed we were getting to the start of geni_i2c_rx_one_msg() but were > never executing geni_se_rx_dma_prep(). > > I believe that the problem here is that we are writing the transfer > length and setting up the geni command before we run > geni_se_rx_dma_prep(). If a transfer makes it far enough before we do > that then we get into the state I have observed. Let's change the > order, which seems to work fine. > > Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller") > Signed-off-by: Douglas Anderson > --- Reviewed-by: Akash Asthana -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project