On Tue, Jan 10, 2017 at 05:17:07PM +0000, Ryan Harkin wrote:
On 10 January 2017 at 16:58, Alexander Graf agraf@suse.de wrote:
On 01/10/2017 05:47 PM, Ryan Harkin wrote:
I have a background task to refactor u-boot support for ARM Ltd boards. One of many options I was considering was to have a minimal DTB to configure the platform with only the nodes needed for u-boot. The ARM Ltd device trees fluctuate so much, I wouldn't be able to commit to one DTB that will work forever...
No, it's only meant as a fallback when no manual device tree is provided.
Thanks for confirmation.
In an ideal world however, device trees are static and complete, so you could just put a final dt into U-Boot and have it propagated all the way through.
I look forward to living in this ideal world the EDK2 and kernel communities promised me several years ago ;-)
To be fair, the *upstream* DTs for ARM Ltd platforms are relatively stable. I must assume you're talking about random platform trees from elsewhere, which it's not fair to blame the EDK2 or Linux communities for. ;)
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.
It's certainly not great that those aren't in a separate canonical repo, but in terms of stability we are largely there, random *not upstream* platform trees notwithstanding. We'll never get complete from day one, so some updates over time are a fact of life, but we are in the position to ship something that continues to work...
Thanks, Mark.