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    Subject[PATCH v2 2/2] doc: dt: mtd: add a DT property to enable the use of 4byte-address op codes
    Date
    This patch adds a new optional DT property which enables an alternative
    way of supporting memory size above 16MiB (128Mib). This new mechanism
    translates the regular 3byte-address op codes into their 4byte-address
    version whereas the old/default mecanism makes the SPI memory enter its
    4byte-address mode, which has annoying side effects for early bootloaders.

    We cannot discover at run time whether the SPI NOR memory supports the
    4byte-address op codes. For instance both Macronix MX25L25635E and
    MX25L25673G share the same JEDEC ID (C22019 without any extension byte).
    However the first one doesn't support 4byte-address op codes whereas the
    second one does.

    Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
    ---
    Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt | 11 +++++++++++
    1 file changed, 11 insertions(+)

    diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
    index 2c91c03e7eb0..8be610482089 100644
    --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
    +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
    @@ -66,6 +66,17 @@ Optional properties:
    Refer to your chips' datasheet to check if this is supported
    by your chip.

    +- m25p,4byte-opcodes: For memory size above 16MiB (128Mib), use the dedicated
    + 4byte-address opcodes instead of entering the 4byte
    + address mode. This mode changes the internal state of the
    + chip so may conflict with some early boot loaders, which
    + expect to use the regular (Fast) Read opcodes with 3byte
    + address.
    + However 4byte-address opcodes are not supported by all
    + chips and support for them can not be detected at runtime.
    + Refer to you chip's datasheet to check if this is
    + supported by your chip.
    +
    Example:

    flash: m25p80@0 {
    --
    1.8.2.2
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