On 11/10/2017 01:35 PM, Pankaj Bansal wrote:

quoted

quoted

3. Regarding backward compatibility with PowerPC, I see that there is only one platform in PowerPC architecture that is using flexcan.
    There is only one platform in "arch/powerpc/boot/dts/" having flexcan node. p1010si-post.dtsi
    I have added the big-endian property in that platform and have tested it on P1010 platform after backporting the patch to Freescale SDK 1.4 linux.
    I have sent the patch for this. See "[PATCH 2/3] powerpc: dts: P1010: Add endianness property to flexcan node"
    I believe these changes can be accepted for both powerpc and arm and other architectures that use flexcan.

No, this is not acceptable. You break the device tree. Please add the le, be information to the devtype data.

I don't understand how this breaks device tree? can you please elaborate? This method is already being used in other specifications.

Boot a new kernel with an old tree on a PPC board -> flexcan will not work.

See this talk for more information for stable device tree ABI:

https://elinux.org/images/0/0e/OSELAS.Presentation-ELCE2017-DT.pdf
https://www.youtube.com/watch?v=6iguKSJJfxo

You can refer "Documentation/devicetree/bindings/usb/usb-ehci.txt" or
"Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt" Or
"Documentation/devicetree/bindings/regmap/regmap.txt".

In my opinion, keeping this info in devtype data is not good idea.
E.g. say two platforms which have same FlexCAN hardware revision,
will have same quirks. BUT these two platforms implement FlexCAN in
le and be fashion respectively.

Then it's two different platforms. Simply add another compatible to the
driver.

With current FlexCAN driver, these two platforms can have same
devtype data. And we need not to change flexcan.c if we want to add
support for a second platform. We can just add device tree for that
platform (which would be needed anyway), and it can work. We can
mention endianness in device tree.

Marc

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