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Bug#731345: flash-kernel: add support for DT based kernels on Sheeva Plug



On 12/05/2013 01:15 PM, Ian Campbell wrote:
> On Thu, 2013-12-05 at 13:04 +0100, Marc Kleine-Budde wrote:
>> On 12/05/2013 12:57 PM, Ian Campbell wrote:
>>> On Thu, 2013-12-05 at 12:46 +0100, Marc Kleine-Budde wrote:
>>>> On 12/05/2013 12:34 PM, Martin Michlmayr wrote:
>>>>> * Marc Kleine-Budde <mkl@blackshift.org> [2013-12-05 11:49]:
>>>>>> That's no option, as non DT Sheeva Plug support has been removed from
>>>>>> the kernel in ffbc50663b69462adc9d97b93b6b92c4fe74b94c:
>>>>>>
>>>>>> ffbc506 ARM: kirkwood: remove support for legacy booting of Sheevaplug
>>>>>
>>>>> Interesting.  I thought they promised not to remove non-DT support for
>>>>> existing devices.
>>>>
>>>> I personally don't mind, if it's removed once the DT works properly.
>>>>
>>>>> Anyway, Marc, so thanks for your patch.  I wonder if it makes sense to
>>>>> add a check to flash-kernel whether DT is required or not.  i.e. that
>>>>> flash-kernel would append the DT blob on 3.12+ kernels on SheevaPlug
>>>>> but not on previous kernels.
>>>>
>>>> Yes, sounds like the way to go. Otherwise you have to tie certain
>>>> flash-kernel versions to the non-DT and DT kernels. This will probably
>>>> not scale when more no-DT board are removed from the kernel.
>>>>
>>>> Where should this information go? What about adding another field to
>>>> all.db which limits an entry to certain kernel versions? Something like
>>>> this:
>>>
>>> I think it would be sufficient to have a field marking the DTB as
>>> optional and have f-k only do the append if there is a dtb present in
>>> the DTS directory (/usr/lib/linux-X.Y/whatever) for the version it is
>>> handling. If the kernel needs a DTB but doesn't ship one, well ,that's a
>>> bug in the kernel (until we get to the point of burning DTBs into
>>> firmware, but lets not worry about that now!).
>>
>> ...or when the DT sources will be move into a separate repository.
> 
> Indeed.
> 
> Actually, now that I think about it -- a non-DT aware kernel just
> shouldn't care if you append a DT to it, it won't ever go looking. It's
> probably safe to just append it unconditionally.

Yes, should be safe.

> Which is what you did, so we've come full circle, sorry for the
> distraction.

It's good to talk about the implications. If we want to handle
downgrading of kernels with an updated flash-kernel, I think, that
cannot be done without an additional Kernel-Version field.

This is because v3.11 ships with:

/usr/lib/linux-image-3.11-2-kirkwood/kirkwood-sheevaplug.dtb

But non-DT Sheeva support is still in the kernel, so non-DT Sheeva Plug
is used with current flash-kernel and v3.11. Although v3.10 and v3.11
are not Wheezy's kernels.

> I suppose it would be nice to just check that the Wheezy kernel doesn't
> complain about or get confused by the appended DTB. Can you check that?

I don't have physical access to that Sheeva Plug.

Marc

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