On Thu, Jan 12, 2017 at 01:47:32PM +0000, Ryan Harkin wrote:
> On 12 January 2017 at 12:25, Mark Rutland <mark.rutl...@arm.com> wrote:
> > On Tue, Jan 10, 2017 at 06:50:19PM +0000, Jon Medhurst (Tixy) wrote:
> >> On Tue, 2017-01-10 at 18:34 +0000, Mark Rutland wrote:
> >> > Looking at the git log for arch/arm64/boot/dts/arm, most updates are
> >> > simply adding new descriptions, so a DTB from a year ago should work
> >> > just fine with mainline (modulo the Juno PCI window issue, which was a
> >> > DTB bug). Upgrading kernel shouldn't require a DTB upgrade to see
> >> > equivalent functionality.

> > The key point is that it is possible to provide a baseline DTB that is
> > good enough for most users, and will work with future kernels.
> >
> > We're unlikely to get to a state where DTBs are perfect and complete
> > from day one. We can have something that remains usable.
> I hope it stays that way. Most of my users are either on 3.18 or 4.4.
> And they are incompatible with each other w.r.t. DTBs to the point
> where one won't even post a banner message with the other's DTB.

Interesting. Just to check, do you mean v3.19? There was no upstream
Juno DT in v3.18.

Unfortunately, I can't spot any DT changes between v3.19 and v4.4 that
would obviously break compatibility such that serial wouldn't work.

If you have those kernels && DTBs to hand, are you able to take a look
if passing "earlycon=pl011,0x7ff80000"?

I know that the ARM Software linux repo shipped a broken DT, along with
some kernel modifications which bodge around that (specifically, they
exposed a broken MMIO timer as functional). IIRC, Poking that would
bring down the kernel, before the serial wa up.

Is your v3.18 DT the old ARM Software repo's Juno DT?

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