[fedora-arm] Quick notes from Sunday....

[Peter Robinson]

On Sun, Jan 20, 2013 at 10:50 PM, Nicolas Pitre <nico at fluxnic.net> wrote:
> On Sun, 20 Jan 2013, Jon wrote:
>
>> On Sun, Jan 20, 2013 at 8:34 PM, Jonathan Masters <jcm at redhat.com> wrote:
>>
>> >    - dtb. Need to get dtb built into 3.6 based F18 RC images in order to
>> > be ready for 3.7. Especially OMAP and Tegra. Dennis prefers built in
>> > standard package, ok with doing so in 3.7 kernel (kernel-dtb) and pulling
>> > back into RC images as an exception this one time. Saves reissuing 3.6
>> > kernel package. Some testing done. Need to verify all targets have right
>> > bits in place and check 3.7 kernel upgrade.
>> >
>> >
>> Today I tried to get the pandaboard to boot using the 3.6 DTB from ausil
>> website, and was not successful loading the DTB from u-boot load addr.
>> I suspect for panda we might have to append the DTB to the zimage and run
>> mkimage on it.
>> That would be a great task for grubby or whatever part of the kernel
>> install that invokes mkimage.
>
> Please don't do that (the DTB append that is).  This is a convenience
> for platform where it is impossible to update the bootloader in order
> to accommodate a DTB.  A Pandaboard certainly does not fall into that
> category.
>
> And this DTB append is not something I'd advise Fedora to ever support
> unless there is absolutely no other way.  Most of the Fedora ARM targets
> should have other ways.
>
> U-Boot has had native device tree on ARM for quite a while now.  Please
> ensure that the U-Boot version on your Panda is sufficiently recent.

It's the latest 2012.10 upstream release, it that sufficiently recent?
But I agree on panda/beagle where we use the upstream I believe from
my reading the uboot should be supplying the DT blob so it should
"just work" the question is why isn't it and how do we tell if uboot
is supplying a DT blob?

I've done a lot of googling and reading but while there's a lot of
good resources for kernel driver developers for DT there's not really
a good resource that I've found for distro side and how to deal with
DT, how to check the uboot (or OFW or what ever other boot loader)
supplies a DT and whether it is good or not. Is there a way to see it
via /proc or /sys or some other means? Commands to print it from
uboot? Anything we need to specify in the kernel to ensure it attempts
to retrieve it first from the boot loader and a way to fail back if it
doesn't?

Peter