Re: [PATCH 02/13] hw/ide/via: Implement ISA IRQ routing

[BALATON Zoltan]

On Mon, 24 Apr 2023, Bernhard Beschow wrote:
> Am 22. April 2023 19:21:12 UTC schrieb BALATON Zoltan <balaton@eik.bme.hu>:
> > On Sat, 22 Apr 2023, Bernhard Beschow wrote:
> > > Am 22. April 2023 17:23:56 UTC schrieb BALATON Zoltan <balaton@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.
>
> Indeed. I've updated my copy of the datasheet.
>
> > > > 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.
>
> I'll try to find the Debian ISO to test with pegasos2.rom.

It should be here I think:
https://www.debian.org/releases/jessie/debian-installer/

Regards,
BALATON Zoltan

> > > 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.
>
> I see it now. I'll use hardcoded IRQs 14 and 15 then.
>
> Best regards,
> Bernhard
>
> > Regards,
> > BALATON Zoltan