64-bit RPi4B u-boot hangup with modern rpi firmware: some information (but investigative-toolbox limited)

[Mark Millard]

On 2020-Oct-14, at 00:22, Mark Millard <marklmi at yahoo.com> wrote:

> On 2020-Oct-13, at 23:18, Klaus Cucinauomo <maciphone2 at googlemail.com> wrote:
> 
>> Am 14.10.2020 um 07:52 schrieb Mark Millard <marklmi at yahoo.com>:
>>> 
>>> …...FreeBSD requires services from
>>> armstub8-gic.bin that are not otherwise present as things
>>> are (or that is my understanding).
>> 
>> as of today:  correct understanding
>> 
>>> 
>>> ... I'll test vintages of start4*.elf and fixup4*.dat
>>> pairs and see if that identifies a specific set of changes
>>> to them...
>> 
>> IIRC „we" can hack armstubs but  we cannot hack  start4*.elf &  fixup4*.dat ,
>> but you can take a hexdump of start4*.elf  to compare changes  if you feel like it,
>> while I doubt that will easy find the cause(s)..
> 
> hexdump comparisons is not something I'm likely to do and is
> not what I said I was going to do.
> 
> Types of changes are identified by the commit notes. It is
> possible with what I'm doing that a firmware problem would
> be identified that the rpi folks would work on. (Not
> claiming to know it is likely or anything.)

Turns out that FreeBSD is not the only context with problems,
others not involving armstub8-gic.bin or FreeBSD at all are
also having (a sequence of) problems. See, for example, the
sequence of notes in:

https://github.com/raspberrypi/firmware/issues/1445

where problems showed up in contexts using edk2's uefi
for RPi4's and, separately, for RPi3's.

The known issues are being worked on. (I've no evidence
at this point relative to sufficiency for FreeBSD's context.)

> I've already reported on the lists a patch for u-boot 2020.10
> not avoiding stomping on memory owned by the armstub8-gic.bin
> that FreeBSD uses. (It is not guaranteed to stomp on such
> memory either: u-boot just does not reserve the memory area
> that it should and so treats it as available for potential
> use.)
> 
> If I had only focused on armstub8-gic.bin I never would have
> found that problem. (Of course, if armstub8-gic.bin ends up
> eliminated, the problem I found goes away too.)
> 
> Unfortunately, the patch does not fix the symptoms that
> started this effort but the defect could lead to problems.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)