Bug#731345: flash-kernel: add support for DT based kernels on Sheeva Plug
On Thu, 2013-12-05 at 13:39 +0100, Marc Kleine-Budde wrote:
> 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.
Is 3.11+DTB actively broken though?
> > 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.
Hrm, this would be something which would be good to try somewhere.
Now I think of it the Wheezy kirkwood kernel did have DT and
APPENDED_DTB support enabled, in order to support dreamplugs.
I have a feeling that would mean that it wouldn't boot if you appended a
dtb to it. Which would mean we do have to think about versioned checks
or something.
Ian.
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