[U-Boot] [PATCH 19/26] configs: mx6sabresd: Add SPL FIT and DM support

[Tom Rini]

On Fri, Jan 18, 2019 at 03:26:42PM +0000, Abel Vesa wrote:
> On 19-01-18 13:16:07, Fabio Estevam wrote:
> > Hi Abel,
> > 
> > On Fri, Jan 18, 2019 at 12:59 PM Abel Vesa <abel.vesa at nxp.com> wrote:
> > 
> > > +CONFIG_OF_CONTROL=y
> > > +CONFIG_SPL_OF_CONTROL=y
> > > +CONFIG_DEFAULT_DEVICE_TREE="imx6q-sabresd"
> > 
> > Does this mean that only imx6q-sabresd variant is supported after this
> > series is applied?
> > 
> > We still need to support imx6dl/imx6qp sabresd in the same binary as
> > we currently do today.
> 
> Hmmm, so all the dtbs get built, trouble is we need to specify which dtb gets
> used by SPL. This is why the DEFAULT_DEVICE_TREE gets set.
> 
> A solution to do what you're asking is to have a dtb in SPL that works for
> all socs (dl/qp/q) for each board (sabreauto/sabresd). I'm afraid it might
> get too big to fit in sram. I'll give it a try tomorrow.
> 
> As for the u-boot proper, in order to have one u-boot.itb file that works
> on all socs we need to support MULTI_FIT in u-boot proper and make u-boot
> chose from the fit table the right dtb. I'll try to do that for the next
> version of this patchset. I'll keep you up to date with the development.

Please note that this isn't the first family to have this problem.
Please see the TI Keystone 2 families and CONFIG_DTB_RESELECT as I would
swear we can go from a "good enough for all" to "correct for what we're
on" DTB in both SPL and U-Boot.  And then yes, you end up compressing
the DTBs too so that we can fit things into limited space.  And if we
still run into problems, which we might well still, lets talk.  And it
might indeed end up making the most sense to make up a "just enough for
SPL for everyone" DTB or set of DTBs too.

-- 
Tom
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