Re: [PATCH 2/2] via-ide: Also emulate non 100% native mode

[BALATON Zoltan]

On Fri, 6 Mar 2020, Mark Cave-Ayland wrote:
> On 05/03/2020 23:35, BALATON Zoltan wrote:
> > On real hardware this may be true but in QEMU how would it otherwise raise the
> > correct interrupt line the guest expects? This probably does not matter for 
> > pegasos2
> > but I think is needed for 100% native mode used with the fulong2e so it gets 
> > the IRQ
> > it expects.
>
> That's easy - remember that both the PCI and IRQ interrupts are separate pins 
> on the
> chip, so all that needs to be done is expose the legacy IRQ via qdev and use 
> that to
> wire it up to your interrupt controller.

This "chip" is part of an integrated southbridge/superio/everything chip 
the also includes the two PICs and how they are internally connected is 
not known so we would be guessing here anyway. I don't see a need to make 
it more complicated than it is now by modeling internal pins but how would 
I wire up gpio to the i8259 model and where should I connect the PCI irq?

> Okay so this is interesting: I've been switching between the VT8231 and the 
> VT82C686B
> datasheets, and there is a difference here. You are correct in what you say 
> above in
> that the 8231 docs specify that this is set to 1, but on the 686B this is 
> clearly not
> the case.

The 82C686B says this reg can be 0 or 1, where 0 is legacy interrupt 
routing and 1 is native mode. Given that we only model native mode of the 
chip it does not make sense to set it to anything else than 1 and setting 
it to 0 confuses MorphOS and Linux on pegasos2 while setting it to 1 works 
with everything I've tried both on pegasos2 and fulong2e even if that may 
not completely match how it's implemented in hardware.

> What is rather unusual here is that both the 8231 and 686B have exactly the same
> device and vendor ids, so I'm not sure how you'd distinguish between them?

Guests distinguish by looking at the parent device (function 0) which is 
the chip this IDE device is part of (on function 1).

Regards,
BALATON Zoltan