Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Esben Haabendal <esben.haabendal@gmail.com>
To:     Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
Cc:     linux-i2c@vger.kernel.org,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Phil Reid <preid@electromag.com.au>,
        Linus Walleij <linus.walleij@linaro.org>,
        Clemens Gruber <clemens.gruber@pqgruber.com>,
        Wei Jinhua <wei.jinhua1@zte.com.cn>,
        Michail Georgios Etairidis <m.etairidis@beck-ipc.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] i2c: imx: Fix race condition in dma read
References: <20180523095623.3347-1-esben.haabendal@gmail.com>
        <20180523095623.3347-3-esben.haabendal@gmail.com>
        <20180705063229.sr6jplg63ybyzxta@pengutronix.de>
Date:   Mon, 09 Jul 2018 11:22:31 +0200
In-Reply-To: <20180705063229.sr6jplg63ybyzxta@pengutronix.de> ("Uwe
        =?utf-8?Q?Kleine-K=C3=B6nig=22's?= message of "Thu, 5 Jul 2018 08:32:29
 +0200")
Message-ID: <87tvp8ahm0.fsf@gmail.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Uwe Kleine-K=C3=B6nig <u.kleine-koenig@pengutronix.de> writes:

> On Wed, May 23, 2018 at 11:56:21AM +0200, Esben Haabendal wrote:
>> From: Esben Haabendal <eha@deif.com>
>>=20
>> 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 genera=
ted
>> to kickstart the DMA read, and a timeout happens after DMA_TIMEOUT (1 se=
c).
>>=20
>> Fixed by setting the DMAEN bit before the dummy read.
>
> Does this fix the problem or just narrow the race window?

It should fix the problem.

/Esben