Re: [PATCH v4 00/11] An effort to bring DT bindings compliance within U-Boot

[Andre Przywara <andre.przywara@arm.com>]

On Mon, 22 Jan 2024 11:49:59 -0500
Tom Rini <trini@konsulko.com> wrote:

Hi Tom,

> On Mon, Jan 22, 2024 at 11:45:15AM +0000, Andre Przywara wrote:
> > On Wed, 10 Jan 2024 16:05:36 +0530
> > Sumit Garg <sumit.garg@linaro.org> wrote:
> > 
> > Hi,
> > 
> > I certainly welcome this more automatic synchronisation of the DTs,
> > however have one comment about the upcoming sync process:
> >   
> > > ...
> > > However, Linux kernel DT maintainers proposed [2] for U-Boot to rather
> > > use devicetree-rebasing repo [3] which is a forked copy from Linux
> > > kernel for DT source files as well as bindings. It is tagged at every
> > > Linux kernel major release or intermideate release candidates. So here I
> > > have tried to reuse that to bring DT bingings compliance as well as a
> > > standard way to maintain a regular sync of DT source files with Linux
> > > kernel.
> > > 
> > > In order to maintain devicetree files sync, U-Boot will maintains a Git
> > > subtree for devicetee-rebasing repo as `dts/upstream` sub-directory.
> > > U-Boot will regularly sync `dts/upstream/` subtree whenever the next window
> > > opens with the next available kernel major release.  
> > 
> > I hope this doesn't need to stay that restricted? Can we either sync more
> > often, or at least on the kernel's -rc1, and not only on a "full" release?
> > 
> > The reason I ask is that we have a chicken-egg problem here: without a DT
> > merged into the kernel tree, no U-Boot board support can be merged. And
> > without U-Boot support, we cannot boot a kernel, at least not in the
> > canonical way.
> > 
> > Since the U-Boot and kernel merge windows are not in phase, for sunxi I try
> > to sync the kernel DTs either as early as possible (-rc1, sometimes even
> > before, when the maintainers have merged them into their tree), or
> > sometimes "out of season", if a board defconfig patch is coming up.
> > 
> > Otherwise new board support, which typically has a very low regression risk
> > for the rest of the code base, would need to be delayed until the next
> > release. In the worst case the U-Boot merge windows opens one week before
> > a kernel release, then new boards need to wait three months?  
> 
> Would it be to bad to bring in board X with OF_UPSTREAM=n for one U-Boot
> release, and then with the next one switch to OF_UPSTREAM=y (and delete
> the dts from arch/) for the next release, when we would have gotten back
> in sync?

Ah, I didn't look into the actual patches, but if this provision is
there, that sounds surely acceptable. It might still be good to sync
earlier than the .0 kernel release: if it appears in Linus' tree, it
had already seen a good share of review and testing. And with the
U-Boot releases being always further away than the next kernel release,
we could pull fixes still in time. So we could pick the latest -rc (or
.0 release, whichever is more recent) when the U-Boot merge window
opens?

Cheers,
Andre