On Sat, 22 Apr 2023, Bernhard Beschow wrote:
Am 22. April 2023 17:23:56 UTC schrieb BALATON Zoltan <bala...@eik.bme.hu>:
On Sat, 22 Apr 2023, Bernhard Beschow wrote:
The VIA south bridge allows the legacy IDE interrupts to be routed to four
different ISA interrupts. This can be configured through the 0x4a register in
the PCI configuration space of the ISA function. The default routing matches
the legacy ISA IRQs, that is 14 and 15.
On VT8231 0x4a is PCI Master Arbitration Control, IDE interrupt Routing is 0x4c
and only documents 14/15 as valid values.
In the datasheet titled "VT8231 South Bridge", preliminary revision 0.8,
Oct. 29, 1999, page 60, the "IDE Interrupt Routing" register is located
at offset 0x4a and offers the same four interrupts in the same order as
in the code. Are we looking at the same datasheet?
Apparently not. The one I have says: Revision 2.32, May 10, 2004. Looks
more authorative than a preliminary one.
Not sure any guest would actually change this or 0x4a and if that could cause
problems but you may need to handle this somehow. (Apart from testing with
MorphOS with -kernel you should really be testing with pegasos2.rom with
MorphOS and Linux, e.g. Debian 8.11 netinstall iso is known to boot.)
I've tested extensively with an x86 Linux guest on my pc-via branch which
worked flawlessly.
That does not substitute testing Linux on pegasos2 though becuase there
are some hacks in Linux kernel to handle some pecularities of the pegasos2
including via ide on that machine and that can only be fully tested with
pegasos2.rom and PPC Linux.
As mentioned in the commit message the default routing of the chipset
matches legacy behavior, that is interrupts 14 and 15. This is reflected
by assigning [0x4a] = 4 in the code and that is how the code behaved
before.
And that's the only allowed value on VT8231, other bits are listed as
reserved so I wonder if we want to model this at all if no guest is
touching it anyway. So you could also just drop that part and keep it hard
mapped to 14-15 as it is now, mentioning the config reg in a comment if we
ever find a guest that needs it.
Regards,
BALATON Zoltan
