From: Rob Herring <robh@kernel.org>
To: "Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>
Cc: wsa@the-dreams.de, linux-i2c@vger.kernel.org,
linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH] i2c: rcar: add DMA support
Date: Thu, 5 May 2016 17:06:25 -0500 [thread overview]
Message-ID: <20160505220625.GA18367@rob-hp-laptop> (raw)
In-Reply-To: <1462365503-8451-1-git-send-email-niklas.soderlund+renesas@ragnatech.se>
On Wed, May 04, 2016 at 02:38:23PM +0200, Niklas Söderlund 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 done
> via DMA.
>
> 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 condition
> for DMA reception.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> 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 <robh@kernel.org>
next prev parent reply other threads:[~2016-05-05 22:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-04 12:38 [PATCH] i2c: rcar: add DMA support Niklas Söderlund
2016-05-05 22:06 ` Rob Herring [this message]
2016-05-12 21:35 ` Wolfram Sang
2016-05-12 21:31 ` Wolfram Sang
2016-05-14 12:12 ` Niklas Söderlund
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