Re: [PATCH linux-next v2 1/4] ARM: at91/dt: add a new DT property to support FIFOs on Atmel USARTs

[Alexandre Belloni <alexandre.belloni@free-electrons.com>]

On 11/06/2015 at 18:20:14 +0200, Cyrille Pitchen wrote :
> This patch adds a new DT property, "atmel,fifo-size", to enable and set
> the maximum number of data the RX and TX FIFOs can store on FIFO capable
> USARTs.
> 
> Please be aware that the VERSION register can not be used to guess the
> size of FIFOs. Indeed, for a given hardware version, the USARTs can be
> integrated on Atmel SoCs with different FIFO sizes. Also the
> "atmel,fifo-size" property is optional as older USARTs don't embed FIFO at
> all.
> 
> Besides, the FIFO size can not be read or guessed from other registers:
> When designing the FIFO feature, no dedicated registers were added to
> store this size. Unsed spaces in the I/O register range are limited and
> better reserved for future usages. Instead, the FIFO size of each
> peripheral is documented in the programmer datasheet.
> 
> Finally, on a given SoC, there can be several instances of USART with
> different FIFO sizes. This explain why we'd rather use a dedicated DT
> property than use the "compatible" property.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com