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    SubjectRe: [PATCH v3 2/3] spi: atmel: update DT bindings documentation
    Le 09/06/2015 19:25, Mark Brown a écrit :
    > On Tue, Jun 09, 2015 at 01:53:53PM +0200, Cyrille Pitchen wrote:
    >> - add new property "atmel,fifo-size"
    >
    > Why is this a property and not something we know from the IP version?
    >
    Hi Mark,

    Please be aware that the VERSION register can not be used to guess the
    size of FIFOs. Indeed, for a given hardware version, the SPI controller
    can be integrated on Atmel SoCs with different FIFO sizes. Also the
    "atmel,fifo-size" property is optional as older SPI controllers 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. Unused 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 the SPI
    controller with different FIFO sizes. This explain why we'd rather use a
    dedicated DT property than use the "compatible" property.

    I hope these pieces of information will help to clarify this point.
    Of course, we are open to other suggestions.

    Best Regards,

    Cyrille


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