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[87.57.30.174]) by smtp.gmail.com with ESMTPSA id q65-v6sm1447807lfb.80.2018.07.09.02.22.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 09 Jul 2018 02:22:32 -0700 (PDT) From: Esben Haabendal To: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= Cc: linux-i2c@vger.kernel.org, Wolfram Sang , Lucas Stach , Phil Reid , Linus Walleij , Clemens Gruber , Wei Jinhua , Michail Georgios Etairidis , 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Uwe Kleine-K=C3=B6nig writes: > On Wed, May 23, 2018 at 11:56:21AM +0200, Esben Haabendal wrote: >> From: Esben Haabendal >>=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