From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH] i2c: rcar: add DMA support Date: Thu, 5 May 2016 17:06:25 -0500 Message-ID: <20160505220625.GA18367@rob-hp-laptop> References: <1462365503-8451-1-git-send-email-niklas.soderlund+renesas@ragnatech.se> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1462365503-8451-1-git-send-email-niklas.soderlund+renesas@ragnatech.se> Sender: linux-i2c-owner@vger.kernel.org To: Niklas =?iso-8859-1?Q?S=F6derlund?= Cc: wsa@the-dreams.de, linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org On Wed, May 04, 2016 at 02:38:23PM +0200, Niklas S=F6derlund wrote: > Make it possible to transfer i2c message buffers via DMA. > Start/Stop/Sending_Slave_Address and some data is still handled using > the old state machine, it is sending the bulk of the data that is don= e > via DMA. >=20 > The first byte of a transmission and the last two bytes of reception = are > sent/received using PIO. This is needed for the HW to have access to = the > first byte before DMA transmit and to be able to set the STOP conditi= on > for DMA reception. >=20 > Signed-off-by: Niklas S=F6derlund > --- > Documentation/devicetree/bindings/i2c/i2c-rcar.txt | 3 + > drivers/i2c/busses/i2c-rcar.c | 237 +++++++++++= +++++++++- > 2 files changed, 236 insertions(+), 4 deletions(-) Is DMA actually faster or less cpu usage? I'm doubtful. Acked-by: Rob Herring