[PATCH 2/8] i2c: at91: add warning about transmission issues for some devices

[Voss, Nikolaus]

ludovic.desroches at atmel.com wrote on Friday, August 31, 2012 11:21 AM
> From: Ludovic Desroches <ludovic.desroches at atmel.com>
> 
> Some devices don't have clock streching in transmission mode. It can
> lead to premature stop sendings if the latency to write data in the
> transmission register is too long. In this case, prefer the i2c-gpio
> driver.
> 
> Signed-off-by: Ludovic Desroches <ludovic.desroches at atmel.com>
Acked-by: Nikolaus Voss <n.voss at weinmann.de>

> ---
>  drivers/i2c/busses/Kconfig | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index d9c4918..da77c37 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -300,6 +300,12 @@ config I2C_AT91
>  	  to support combined I2C messages.  Use the i2c-gpio driver
>  	  unless your system can cope with this limitation.
> 
> +	  Caution! at91rm9200, at91sam9261, at91sam9260, at91sam9263
> devices
> +	  don't have clock stretching in transmission mode. For that reason,
> +	  you can encounter underrun issues causing premature stop
> sendings if
> +	  the latency to fill the transmission register is too long. If you
> +	  are facing this situation, use the i2c-gpio driver.
> +
>  config I2C_AU1550
>  	tristate "Au1550/Au1200/Au1300 SMBus interface"
>  	depends on MIPS_ALCHEMY
> --
> 1.7.11.3