Re: Several Malta patches developed using QEMU

["Maciej W. Rozycki" <macro%orcam.me.uk@localhost>]

On Sun, 29 Mar 2026, Thor Lancelot Simon wrote:

> The patches below address a number of issues I found while trying to ensure
> that all 4 combinations of byte order and word size worked properly with
> our MALTA/MALTA64 kernels and QEMU's malta system emulation.  THEY HAVE NOT
> BEEN TESTED ON REAL HARDWARE - if anyone still has any, which someone likely
> does.

 I do.

> Most of the issues center around either endianness issues with the Gallileo
> host bridge, or the lack of initialization that would be performed by the
> YAMON firmware on real hardware, particularly when using QEMU's "-kernel"
> option to directly load the kernel.  I don't think these patches contain
> anything that would break real hardware, but, if anything, it might be
> the PCI IRQ initialization.

 Umm, sadly my GT64120A-based core card has stopped working a couple years 
ago after 20 years in service, and so far I have failed to bring it back 
to life -- it does not come out of reset and while the 5Kc CPU's TAP port 
does respond over EJTAG, the CPU core itself is reported off-line.  I have 
little hope to get it repaired at this point, as the key parts relevant 
here are nowhere to be found (the CPU is an LV, so a special order and not 
a regular part, and the bitfile for the Altera EPLD has been lost AFAIK).

 I can run stuff with SOC-it or ROC-it core cards though in case it helps, 
with any of the 74Kc, 74Kf, or interAptiv CPU.  Obviously it means 32-bit 
only too.

> I'd like to commit these in the next few days.  Comments welcome and if
> anyone has a real Malta board and can test big-endian operation in particular
> I'd love to know whether it works.

 I've never run NetBSD on a Malta, what would I need to do?  Endianness is 
not an issue, there's a switch on board.  Though I tend to run the boards 
in the big-endian mode anyway, as it exposes more issues and I have other 
hardware for little-endian MIPS coverage.

 NB I fiddled with this stuff as my day job back at MIPS UK 20 years ago.  
Obviously I can't remember the details anymore, but I may be able to chase 
things if you find yourself stuck.  Only the loss of the Galileo core card 
is regrettable, as now I'm unable to run anything specific to that system 
controller anymore, or anything 64-bit on a real Malta.

  Maciej