re: SGI O2 unable to boot 9.0+ (status update)

[matthew green <mrg%eterna23.net@localhost>]

looking at the total diff, i see two parts that affect sgimips:

- in start: the bits set in cop0 status change.  before, we
  disabled all but MIPS_SR_BEV (0x400000), then wrote "zero" to
  it to disable interrupts as well.
  now, we clear everything but MIPS_SR_INT_IE (0x1), then keep
  bits (MIPS_SR_TS | MIPS3_SR_RE) (0x200000 | 0x2000000), except
  we already cleared those bits just above"(!!!).  this ends up
  writing zero to cop0 status, like old i guess.

  in both cases, we'd then write 0 to cop0 cause.

  so the main different will be maybe writing 0 or 0x400000,
  then 0, vs maybe writing 0 or 1, and then 0.

- the code to fetch the fpuid now enables MIPS_SR_COP_1_BIT
  (0x20000000) in cop0 status before reading MIPS_FIR.


where the other mips changes around this time besides locore.S?

anyway, it shouldn't too hard to try making these the same as
the old code for sgimips (you can ignore eg new octeon or
hpcmips code, for instance.)  if you're not sure, we can help.


.mrg.

matthew green writes:
> Mike Shields writes:
> > Just thought I'd give a status update on the attempts to get R5k/R10k IP32 sgimips back to life:
>
> > I was able to find the point via bisection, only took about 9 or 10 iterations. On the freebsd-8 branch, the failure starts between 2018-03-07 and 2018-03-08 (a build of 03-97 boots fine, a build of 03-08 freezes after a few lines).
>
> > I have been sifting through the changes, and am finding some updates in src/sys/arch/mips/mips/locore.S to be the most suspicious.
>
> > I am not familiar with R5k/R10k core setup steps, so I'm just fooling around in the dark for now, testing various reversions in that file, but with no success so far.
>
> > I'll keep plugging away, but if any other interested eyes have more familiarity, feel free to bail me out of these depths! ;-)
>
> cc: maya@ who made these changes to locore.S rev's 1.211-1.217.
>
>
> .mrg.
>