[PATCH v3 31/31] RFC: Switch rpi over to use bootstd

[Mark Kettenis]

> Date: Thu, 20 Jan 2022 13:30:47 -0500
> From: Tom Rini <trini at konsulko.com>
> 
> On Thu, Jan 20, 2022 at 11:16:35AM -0700, Simon Glass wrote:
> > Hi Mark,
> > 
> > On Thu, 20 Jan 2022 at 03:29, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> > >
> > > > From: Michael Walle <michael at walle.cc>
> > > > Date: Thu, 20 Jan 2022 09:35:44 +0100
> > > >
> > > > > The bootdevs have a natural priority, based on the assumed speed of
> > > > > the device, so the board would only need to intervene (with an env var
> > > > > or a devicetree property) when that is wrong.
> > > >
> > > > Does this make sense in general? The default boot order for a
> > > > board should depend on what is available on board (or on the
> > > > carrier board) and what is pluggable. I doubt there can be a sane
> > > > default, so almost all boards will have to define its own
> > > > boot order anyway.
> > 
> > Please can you be more specific about what you the problem is here? If
> > the board does not have a device then it will not exist in driver
> > model (or will not probe) and it won't have a bootdev (or it won't
> > probe). That seems to be equivalent to me.
> 
> So, I'm not sure how much of a problem it is, since the board can still
> define the default probe order via environment.  But pick any random SoC
> with more than 1 SD/MMC set of lines on the chip.  Youboard may put the
> first as SD slot and second as eMMC and Myboard may do the opposite and
> both are going to probe in the same order since it's the same chip.
> 
> That's what I think Mark is getting at with it not really making sense
> to just rely on probe order as what to try.

Something like that.  I remember a lot of issues when boards were
switched over to DM_MMC and the boot order changed.  I believe this
ended up beging solved by having aliases in the device tree.