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i2c: rcar: add DMA support

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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>
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
[wsa: fixed a checkpatch warning]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Niklas Söderlund
2016-05-14 14:17:08 +02:00
committed by Wolfram Sang
parent 40027b2fff
commit 73e8b05283
2 changed files with 232 additions and 4 deletions
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3
Documentation/devicetree/bindings/i2c/i2c-rcar.txt
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@@ -19,6 +19,9 @@ Optional properties:
- clock-frequency: desired I2C bus clock frequency in Hz. The absence of this
property indicates the default frequency 100 kHz.
- clocks: clock specifier.
- dmas: Must contain a list of two references to DMA specifiers, one for
transmission, and one for reception.
- dma-names: Must contain a list of two DMA names, "tx" and "rx".
- i2c-scl-falling-time-ns: see i2c.txt
- i2c-scl-internal-delay-ns: see i2c.txt