i2c: rcar: add DMA support
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: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Acked-by: NRob Herring <robh@kernel.org> Tested-by: NWolfram Sang <wsa+renesas@sang-engineering.com> [wsa: fixed a checkpatch warning] Signed-off-by: NWolfram Sang <wsa@the-dreams.de>
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