[U-Boot] [PATCH 3/6] sunxi: add Cubieboard2 support

[Siarhei Siamashka <siarhei.siamashka@gmail.com>]

On Thu, 24 Jul 2014 07:45:44 +0100
Ian Campbell <ijc@hellion.org.uk> wrote:

> On Thu, 2014-07-24 at 06:12 +0300, Siarhei Siamashka wrote:
> > On Thu,  5 Jun 2014 19:00:14 +0100
> > Ian Campbell <ijc@hellion.org.uk> wrote:
> > 
> > > This is a sun7i (A20) based followup to the sun4i (A10)
> > > Cubieboard. It has GMAC using MII mode.
> > > 
> > > Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
> > > Acked-by: Hans de Goede <hdegoede@redhat.com>
> > 
> > This board is using exactly the same PCB as the Cubieboard1. And only
> > the SoC is different (Allwinner A20 instead of the pin-compatible
> > Allwinner A10).
> > 
> > Before piling up more board configurations, we might want to consider
> > supporting both Cubieboard1 and Cubieboard2 with a single u-boot binary
> > (and perhaps keep Cubieboard1 and Cubieboard2 as aliases in boards.cfg).
> > The Allwinner SoCs have support for runtime identification of the SoC
> > type (sun4i/sun5i/sun7i) via the VER_REG (Version Register) located at
> > the address 0x01C00024 as explained in the Allwinner A20 user manual.
> > This requires replacing all the CONFIG_SUN4I/CONFIG_SUN5I/CONFIG_SUN7I
> > ifdefs in the u-boot code with a runtime SoC type checks, but there
> > are not too many places affected (mostly just the DRAM code).
> 
> This all sounds nice but is very certainly a future piece of work not
> related to this patch submission.

The multi-soc support (within the Allwinner A10/A13/A20 family) is the
feature, which is scheduled for this merge window. It is a present
piece of work.

Your patch is related in the sense that it is detrimental to this goal.

> > The newly added Cubieboard2 from your patch appears to be missing the
> > important AXP209_POWER option. So the patch is not good enough to be
> > pushed anywhere in its current form.
> 
> It works for me regardless and always has.

This simply means that your board is not very sensitive to the use of
wrong voltages and may tolerate some abuse. You are just betting on
luck.

If you have been tracking the linux-sunxi mailing list, wrong voltages
(dcdc3 in particular) have caused some very real reliability problems
for some fraction of users. "Works for me" is not the right answer.

> The AXP209 config is trivial to add now that Hans has added the relevant code. 

Yes. You can fix the problem after the fact, or you can avoid pushing
the problematic commit in the first place and do something better.

-- 
Best regards,
Siarhei Siamashka