Re: [PATCH] i2c: rcar: add DMA support

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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@xxxxxxxxxxxx>
> ---
>  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@xxxxxxxxxx>
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