From patchwork Mon Jul 9 09:43:02 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Esben Haabendal X-Patchwork-Id: 941180 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-i2c-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="abi80z4z"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 41PL4q3Fwgz9s00 for ; Mon, 9 Jul 2018 19:43:55 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932743AbeGIJnV (ORCPT ); Mon, 9 Jul 2018 05:43:21 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:43943 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754405AbeGIJnP (ORCPT ); Mon, 9 Jul 2018 05:43:15 -0400 Received: by mail-lj1-f195.google.com with SMTP id r13-v6so13587398ljg.10; Mon, 09 Jul 2018 02:43:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=KoC99XQjYMvYaeFlk1wVGqBun0Bm6WwvjfwbDmoYkF8=; b=abi80z4zuLEZR1FqD25bFzz3m29Z5cWuqrq12SSooGE/+l7sGFR6wuDV4q/l+2/uiI EIOwcu/Su7eOUVSDgpaN9KMJwccelmvx5Os43KG69viR4Fq+V3olFOnV/gwOk3cMfE9B Rc4B2JQYHZvALYRE9wn6wjOvJjWKV3/4DGe02TvSyWygHUggKTfaaQ30NZV7RfSp0EDq WAlXOzYjcCQgv3woJj18s4nSRdjfrV+37n/s/U3q7n1eu7AqexmoyZJ+VGitrehPb6Vb ruuvessCfXpJKjCt3tpyb4hWO3AnqWzKErtLOlHzfHajBjQPXFGtQhA7j2fcRY8J/gq4 4mfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references; bh=KoC99XQjYMvYaeFlk1wVGqBun0Bm6WwvjfwbDmoYkF8=; b=AxXEYKyC2KPXlzrtwfTU1MZVB+wDufCgS+3eAQGpXWVzLfCv9Lw98+N8Q3HaBONaap g5UsEdIFSrEp3fjD5b+a5FqUNL/tw6oAGrN+m6Lxzg0XpaE5giPQLRC09m+CBrhbXieF btsRiTNLPO2IurUpwetyaLinkLB4DG19wDdCQ8IWKrtVszxVZagCNnh8tVf9peOav3f6 abvhwMC7PBiOgK/X4/yVmhi45gbfverNE1asszYlSLPGFTFoD5G+vUUsdW0RRBclyRpq 6n6sUAcN8JN99N4B22vCsjDbAqyReIiAb3iLyV2jqJvPtL0olfPxsil+4zvJZebzHQZD CqHw== X-Gm-Message-State: APt69E1dQzBH34fFePqx0GageaHvlKVvNV54s3s9Hwj8I2WJbuKky3jV JuZFjIxDG79ZJcAW2xVooGcqwoSfYJk= X-Google-Smtp-Source: AAOMgpfga20h+6xcX96OmzEnrWhQ9fCozSdTWMMXwnbaRvjyVysgUJbKCaYIuj90sq9/fVFODhBxlQ== X-Received: by 2002:a2e:40c6:: with SMTP id r67-v6mr12632960lje.41.1531129393815; Mon, 09 Jul 2018 02:43:13 -0700 (PDT) Received: from localhost (87-57-30-174-static.dk.customer.tdc.net. [87.57.30.174]) by smtp.gmail.com with ESMTPSA id v20-v6sm1496115ljc.94.2018.07.09.02.43.12 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 09 Jul 2018 02:43:13 -0700 (PDT) From: Esben Haabendal To: linux-i2c@vger.kernel.org Cc: Wolfram Sang , =?utf-8?q?Uwe_Kleine-?= =?utf-8?b?S8O2bmln?= , Rob Herring , Mark Rutland , Yuan Yao , Esben Haabendal , Fabio Estevam , Lucas Stach , Phil Reid , Clemens Gruber , Peter Rosin , linux-kernel@vger.kernel.org Subject: [PATCH v2 2/4] i2c: imx: Fix race condition in dma read Date: Mon, 9 Jul 2018 11:43:02 +0200 Message-Id: <20180709094304.8814-3-esben.haabendal@gmail.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180709094304.8814-1-esben.haabendal@gmail.com> References: <20180709094304.8814-1-esben.haabendal@gmail.com> Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org From: Esben Haabendal This fixes a race condition, where the DMAEN bit ends up being set after I2C slave has transmitted a byte following the dummy read. When that happens, an interrupt is generated instead, and no DMA request is generated to kickstart the DMA read, and a timeout happens after DMA_TIMEOUT (1 sec). Fixed by setting the DMAEN bit before the dummy read. Signed-off-by: Esben Haabendal --- drivers/i2c/busses/i2c-imx.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 39cfd98c7b23..d86f152176a4 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -668,9 +668,6 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx, struct imx_i2c_dma *dma = i2c_imx->dma; struct device *dev = &i2c_imx->adapter.dev; - temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); - temp |= I2CR_DMAEN; - imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); dma->chan_using = dma->chan_rx; dma->dma_transfer_dir = DMA_DEV_TO_MEM; @@ -810,6 +807,11 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, bo if ((msgs->len - 1) || block_data) temp &= ~I2CR_TXAK; imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); + if (i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data) { + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); + temp |= I2CR_DMAEN; + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); + } imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */ dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);