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    SubjectRe: [PATCH linux-next v2 1/4] ARM: at91/dt: add a new DT property to support FIFOs on Atmel USARTs
    Le 11/06/2015 18:20, Cyrille Pitchen a écrit :
    > 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: Nicolas Ferre <nicolas.ferre@atmel.com>

    > ---
    > Documentation/devicetree/bindings/serial/atmel-usart.txt | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/Documentation/devicetree/bindings/serial/atmel-usart.txt b/Documentation/devicetree/bindings/serial/atmel-usart.txt
    > index 90787aa..e6e6142 100644
    > --- a/Documentation/devicetree/bindings/serial/atmel-usart.txt
    > +++ b/Documentation/devicetree/bindings/serial/atmel-usart.txt
    > @@ -22,6 +22,8 @@ Optional properties:
    > memory peripheral interface and USART DMA channel ID, FIFO configuration.
    > Refer to dma.txt and atmel-dma.txt for details.
    > - dma-names: "rx" for RX channel, "tx" for TX channel.
    > +- atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO
    > + capable USARTs.
    >
    > <chip> compatible description:
    > - at91rm9200: legacy USART support
    > @@ -57,4 +59,5 @@ Example:
    > dmas = <&dma0 2 0x3>,
    > <&dma0 2 0x204>;
    > dma-names = "tx", "rx";
    > + atmel,fifo-size = <32>;
    > };
    >


    --
    Nicolas Ferre


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