linux-kernel - Re: [PATCH 2/4] i2c: imx: Fix race condition in dma read

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Message-ID: <20180705063229.sr6jplg63ybyzxta@pengutronix.de>
Date:   Thu, 5 Jul 2018 08:32:29 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Esben Haabendal <esben.haabendal@...il.com>
Cc:     linux-i2c@...r.kernel.org, Esben Haabendal <eha@...f.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Phil Reid <preid@...ctromag.com.au>,
        Linus Walleij <linus.walleij@...aro.org>,
        Clemens Gruber <clemens.gruber@...ruber.com>,
        Wei Jinhua <wei.jinhua1@....com.cn>,
        Michail Georgios Etairidis <m.etairidis@...k-ipc.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] i2c: imx: Fix race condition in dma read

On Wed, May 23, 2018 at 11:56:21AM +0200, Esben Haabendal wrote:
> From: Esben Haabendal <eha@...f.com>
> 
> 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.

Does this fix the problem or just narrow the race window?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |