[PATCH v2 0/5] i2c: at91: add support to FIFOs and alternative command

Ludovic Desroches ludovic.desroches at atmel.com
Tue Jun 2 01:18:17 PDT 2015

Hi Cyrille,

Could you split the patch about the new alternative command mode?

Reading some comments in your code, you also fixes bad management of the
interrupt flags. It would be great if we can send this as fixes for previous



On Mon, Jun 01, 2015 at 05:49:10PM +0200, Cyrille Pitchen wrote:
> ChangeLog
> v2:
> - fix typo in comment for AT91_TWI_SVEN.
> - document new device tree bindings like "atmel,fifo-size".
> - explicitly set the has_alt_cmd boolean to false to already existing chip
> configs.
> - use the BIT() macro to define the register bits and do a little cleanup in a
> dedicated patch.
> - reword some comments to better explain why the TXCOMP interrupt is no longer
> enabled in at91_do_twi_transfer() but later in
> at91_twi_write_data_dma_callback() to avoid a race condition when DMA is used.
> - remove useless TXCOMP interrupt enable line in at91_twi_write_next_byte()
> since this interrupt is also enabled by at91_do_twi_transfer() for PIO
> transfers.
> v1:
> This series of patches adds support of two new features which will be
> introduced with Atmel sama5d2x SoC.
> First, the alternative command mode eases the sending of STOP conditions.
> Before starting an I2C transaction, the size data to be transfered is
> written into the new Alternative Command Register. For each byte transferred,
> the I2C controller decreases this counter and automatically sends a STOP
> condition when the counter value reaches 0, that is to say when the last byte
> of the transaction has been sent/received. So there is no longer need to set
> the STOP bit into the Control Register.
> Then the use of FIFOs allows to reduce number I/O accesses: for instance,
> the TX FIFO allows to write up to 4 data in a single access to the Transmit
> Holding Register. Also the RX FIFO allows to read up to 4 data in a single
> access to the Receive Holding Register. Currently only DMA transfers take
> advantage of FIFOs.
> Cyrille Pitchen (5):
>   i2c: at91: use BIT() macro to define register bits
>   i2c: at91: update documentation for DT bindings
>   i2c: at91: add support for new alternative command mode
>   i2c: at91: print hardware version
>   i2c: at91: add support to FIFOs
>  Documentation/devicetree/bindings/i2c/i2c-at91.txt |  29 +-
>  drivers/i2c/busses/i2c-at91.c                      | 350 +++++++++++++++++----
>  2 files changed, 318 insertions(+), 61 deletions(-)
> -- 

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