Re: [PATCH] dts: Re-add aliases for imx6qdl-sabrelite devices

[Detlev Casanova <detlev.casanova@collabora.com>]

On Wednesday, December 7, 2022 3:03:56 P.M. EST Tom Rini wrote:
> On Mon, Dec 05, 2022 at 02:33:48PM -0300, Fabio Estevam wrote:
> > On Mon, Dec 5, 2022 at 12:37 PM Tom Rini <trini@konsulko.com> wrote:
> > > I'm not really happy with this approach.  It's not that upstream doesn't
> > > have aliases now, it's that it has different aliases, right? That's why
> > > they won't accept these?
> > 
> > imx6q.dtsi does have the default mmc aliases:
> > 
> > mmc0 = &usdhc1;
> > mmc1 = &usdhc2;
> > mmc2 = &usdhc3;
> > mmc3 = &usdhc4;
> > 
> > Upstream does not want to change mmc alias because users may rely on
> > this mmc aliases.
> > 
> > Changing it now may cause the board not to boot anymore as the rootfs
> > cannot be found.
> > 
> > It is OK to change mmc alias for a newly introduced board, but please
> > keep in mind that
> > wandboard and sabrelite have been launched many many years ago.
> > 
> > So for upstream Linux the message was clear: don't change the mmc
> > alias for these boards.
> > 
> > Now let's talk about U-Boot.
> > 
> > Prior to d0399a46e7cd ("imx6dl/imx6qdl: synchronise device trees with
> > 
> > linux") the mmc alias for sabrelite was present:
> >                mmc0 = &usdhc3;
> >                mmc1 = &usdhc4;
> > 
> > After this commit, the mmc alias is gone and causes the boot
> > regression as reported by Detlev.
> > 
> > We don't want to cause regressions in U-Boot as well, so that's why I
> > propose just adding the alias into u-boot.dtsi.
> > 
> > There are many boards that does the same.
> > 
> > > But this also highlights that we really need to get these kind of
> > > aliases and similar (a) re-synced with upstream ASAP and (b) do that at
> > 
> > imx6 dts files are already synced with Linux.
> > 
> > > the start. I don't know which group of "users are broken by this change"
> > > is bigger, the group that needs the aliases we have or the group that
> > > needs the other aliases, but the group that gets changes upstream first
> > > "wins" here is how the OSS world works.
> > 
> > I prefer to not break things for anyone, hence my proposal.
> > 
> > If you are still not happy with it, please feel free to submit a patch
> > with your proposal.
> 
> I don't know what we can do about the existing boards, but we need to
> NOT do this moving forward. We need to use whatever the aliases are
> upstream already, or upstream the aliases we want to use.

Yes, I agree that aliases should be kept in sync with the kernel. But this 
case is particular because this board has been using different aliases in u-
boot and in linux for some time (maybe since forever).

So this should be kept to avoid breaking existing u-boot setups when they are 
upgraded.