[PATCH v1 0/5] Convert recently merged T30 boards to use DM PMIC

[Thierry Reding]

On Wed, Dec 13, 2023 at 11:42:45AM +0200, Svyatoslav Ryhel wrote:
> 
> 
> 15 листопада 2023 р. 21:11:49 GMT+02:00, Tom Rini <trini at konsulko.com> написав(-ла):
> >On Wed, Nov 15, 2023 at 04:51:08PM +0100, Thierry Reding wrote:
> >> On Mon, Nov 06, 2023 at 04:04:07PM -0500, Tom Rini wrote:
> >> > On Mon, Nov 06, 2023 at 02:11:16PM +0000, Peter Robinson wrote:
> >> > > On Mon, Nov 6, 2023 at 1:28 PM Svyatoslav Ryhel <clamor95 at gmail.com> wrote:
> >> > > >
> >> > > > пн, 6 лист. 2023 р. о 15:13 Peter Robinson <pbrobinson at gmail.com> пише:
> >> > > > >
> >> > > > > On Mon, Nov 6, 2023 at 11:58 AM Svyatoslav Ryhel <clamor95 at gmail.com> wrote:
> >> > > > > >
> >> > > > > > пн, 6 лист. 2023 р. о 13:46 Peter Robinson <pbrobinson at gmail.com> пише:
> >> > > > > > >
> >> > > > > > > Hi Svyatoslav,
> >> > > > > > >
> >> > > > > > > > Since the proposed PMIC patches have been accepted, I see the need
> >> > > > > > > > to convert boards which I maintain to use DM drivers instead of board hacks.
> >> > > > > > > >
> >> > > > > > > > Svyatoslav Ryhel (5):
> >> > > > > > > >   board: lg-x3: convert LG Optimus 4X and Vu to use DM PMIC
> >> > > > > > > >   board: endeavoru: convert HTC One X to use DM PMIC
> >> > > > > > >
> >> > > > > > > Is there a reason why the two above devices don't appear to have their
> >> > > > > > > .dts files in the upstream kernel?
> >> > > > > > >
> >> > > > > >
> >> > > > > > Yes, there is a reason. Linux maintainers treat submitters as
> >> > > > > > existential enemies or as dirt at least. I was trying to work with
> >> > > > > > linux but I have no desire to spend any time to upstream endeavoru or
> >> > > > > > lg_x3.
> >> > > > >
> >> > > > > The usual policy for acceptance into U-Boot is to have upstream review
> >> > > > > in the kernel first.
> >> > > > >
> >> > > >
> >> > > > May you point to a policy which clearly and explicitly states this as
> >> > > > a mandatory condition?
> >> > > 
> >> > > There have been a number of devices rejected in the past until their
> >> > > DT are upstream but I'll leave Tom, who I've explicitly added on cc:,
> >> > > to clarify the exact policy.
> >> > 
> >> > Well, here is where it's tricky. I brought this up for one of the
> >> > Broadcom MIPS platforms a week or two back, and Linus Walleij's point
> >> > (and I'm paraphrasing) is there's not really an upstream for it to go.
> >> > 
> >> > What we cannot have is device tree bindings[1] that aren't upstream or
> >> > worse yet conflict with the official bindings.
> >> > 
> >> > So the general way to resolve that is have device tree file be drop-in
> >> > from the linux kernel, and what additions we must have be done via
> >> > -u-boot.dtsi files. And in turn, some SoCs are better about keeping in
> >> > sync with the kernel than other SoCs are.
> >> > 
> >> > Now, upstream being actively hostile to dts files, especially for older
> >> > platforms? That's unfortunate. So long as we aren't violating the rules
> >> > about bindings, the intention is that we don't have device trees that
> >> > are either (a) massively out of sync with the kernel[2] or (b) kept
> >> > intentionally mismatched from the kernel.
> >> > 
> >> > -- 
> >> > Tom
> >> > 
> >> > [1]: There are both examples like binman that Simon is working on at
> >> > least but this is more exception than intentional rule.
> >> > [2]: Per our other conversions, I know the tegra ones are in this
> >> > unfortunate state in general
> >> 
> >> On the Tegra side we've been fairly lax about the device trees in
> >> U-Boot, I suppose. The assumption had always been that U-Boot would load
> >> an external DTB and pass it to the kernel on boot, so keeping them both
> >> in sync was never a high priority.
> >> 
> >> U-Boot does only a very tiny amount of what Linux does, so dropping in
> >> the kernel DTB always seemed a bit overkill.
> >> 
> >> In either case, if this is problematic, it's something that I could take
> >> a look at. Again, it's expected that the device trees are different, for
> >> historical reasons, but I'd be surprised if they actually conflict with
> >> one another. U-Boot's DTB was always supposed to be a subset of the
> >> Linux DTB.
> >
> >So, the issue with U-Boot and kernel device trees being out of sync is
> >that we then can't support the model of "just pass the current DT to the
> >OS". This in general is good to support because it means that even if a
> >given platform isn't formally SystemReady IR certified it's still likely
> >to be functional.
> >
> >The most strict rule is that you can't have bindings in U-Boot that
> >conflict with the kernel, or should be in the kernel but aren't, and so
> >on.
> >
> 
> So you say that U-Boot should support only components which have linux
> driver? May you clarify?

I think Tom is referring specifically to the bindings only. While it's
certainly preferable to have drivers in Linux for all bindings, that's
never been a strict requirement.

Thierry
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