Re: [PATCH 1/2][v5] dt-bindings: mtd-physmap: Add endianness supports

Boris Brezillon
2018-03-01T17:12:48Z

On Wed, 28 Feb 2018 13:03:34 +0530
Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com> wrote:

> Connection between flash and controller is not necessary to be always
> of same type. It may varies from platform to platform.
>
> Adding endianness (optional) property to provide connection type
> information.
>
> Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> ---
> Changes for v2: updated subject
> Changes for v3: fixed typo for "big-endian"
> Changes for v4: Moved binding definition in mtd-physmap.txt
> as discussed at https://patchwork.ozlabs.org/patch/842543/
> Changes for v5: Sending as it is
>
> Documentation/devicetree/bindings/mtd/mtd-physmap.txt | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mtd/mtd-physmap.txt b/Documentation/devicetree/bindings/mtd/mtd-physmap.txt
> index 4a0a48bf4ecb..961a8eed9d0d 100644
> --- a/Documentation/devicetree/bindings/mtd/mtd-physmap.txt
> +++ b/Documentation/devicetree/bindings/mtd/mtd-physmap.txt
> @@ -41,6 +41,11 @@ additional (optional) property is defined:
>
> - erase-size : The chip's physical erase block size in bytes.
>
> + The device tree may optionally contain endianness property.
> + little-endian or big-endian : It represents connection between controller and
> + flash.

Hm, I'm not even sure it has to do with the HW connection of the data
lines (D0:X), probably more something related to how the flash was
programmed (some people program the flash using a dedicated programmer
before soldering it on the board) and the current platform endianness
(which for some platforms, can be changed with a Kconfig option).

> If this property is absent, flash is considered
> + to be host-endian.

The second sentence is no longer valid. Now, if the property is missing
the behavior is platform/configuration dependent, not necessarily
host-endian.

> +
> The device tree may optionally contain sub-nodes describing partitions of the
> address space. See partition.txt for more detail.
>

--
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering