[U-Boot] U-Boot PXA support

[Simon Glass]

Hi,

On Tue, 21 May 2019 at 08:50, Tom Rini <trini at konsulko.com> wrote:
>
> On Tue, May 21, 2019 at 04:34:19PM +0200, Marek Vasut wrote:
> > On 5/21/19 4:29 PM, Marcel Ziswiler wrote:
> > > On Tue, 2019-05-21 at 14:49 +0200, Marek Vasut wrote:
> > >> On 5/21/19 12:33 PM, Marcel Ziswiler wrote:
> > >>> On Tue, 2019-05-21 at 12:50 +0300, Alex Sadovsky wrote:
> > >>>> It's slightly off-topic but I wonder whether this ongoing
> > >>>> deprecation
> > >>>> of ARMv4 and ARMv5 (first in GCC, then in U-Boot) really
> > >>>> simplifies
> > >>>> anything at all.
> > >>>> There are tons of devices that are still working good and there
> > >>>> are
> > >>>> even ARMv5-based MCUs that are still produced (such as CH561
> > >>>> manufactured by WCH).
> > >>>
> > >>> Please note that as of today Marvell is also still producing them
> > >>> PXAs
> > >>> which are not to go end-of-life before later next year I believe.
> > >>>
> > >>>> IMHO it makes sense to drop only the XScale-specific tuning first
> > >>>> and
> > >>>> to treat PXA (and similar CPUs) as a more generic armv5te. I
> > >>>> wonder
> > >>>> what to do when GCC drops ARMv5 completely...
> > >>>
> > >>> I believe it was only an issue with early gcc 8 but does work just
> > >>> fine
> > >>> again with later 8.2 or 8.3 versions.
> > >>>
> > >>> However, what is more concerning to me is that in today's
> > >>> convoluted
> > >>> moloch known as U-Boot there may simply not be any space any more
> > >>> for
> > >>> something truly embedded but somewhat limited like PXA based
> > >>> hardware.
> > >>
> > >> If we ignore the PXA25x/26x, the PXA27x has loads of SRAM for U-Boot
> > >> SPL
> > >> and then can load U-Boot proper into DRAM. What's the problem ?
> > >
> > > At least on the Colibri PXA270 it is more about NOR flash storage. The
> > > factory configuration block gets stored at an offset of 0x40000 which
> > > leaves only 256 KB for the boot loader. However, of course one could
> > > migrate it all over to using SPL and store U-Boot proper after the
> > > factory configuration block. But to change all that for our very oldest
> > > module which is going end-of-live the next year may not make too much
> > > sense.
> >
> > True
> >
> > > So the real issue with U-Boot for such platforms is basically that the
> > > complexity and footprint increased steadily leaving them behind and
> > > eventually just removing them may be the logical conclusion. After all
> > > we are talking about just a boot loader which is used to boot the
> > > "real" system and good is. However, if even one percent of today's U-
> > > Boot is actually used for booting it is probably already quite a lot
> > > (;-p).
> >
> > The size growth is a problem, even for todays' systems, and it
> > contradicts this "universal" part in U-Boot . That's a real issue which
> > should be addressed , and this fevered push for DM/DT conversion does
> > not help at all.
>
> As I thought I had said before, I think it's really interesting how
> Zephyr takes a DT and spits out a lot of static information.  Taking
> that idea far enough for platforms where no, we don't need any real
> run-time detection of this-or-that could be pretty interesting and
> result in some real space reduction.

I'll reply in a new thread.

Regards,
Simon