Re: [PATCH v5 0/5] VIA PM: Implement basic ACPI support

[BALATON Zoltan]

On Sun, 29 Oct 2023, Bernhard Beschow wrote:
> Am 28. Oktober 2023 17:47:15 UTC schrieb BALATON Zoltan <balaton@eik.bme.hu>:
> > On Sat, 28 Oct 2023, Bernhard Beschow wrote:
> > > Am 28. Oktober 2023 12:58:32 UTC schrieb BALATON Zoltan <balaton@eik.bme.hu>:
> > > > Hello,
> > > >
> > > > On Sat, 28 Oct 2023, Bernhard Beschow wrote:
> > > > > This series is part of my work to bring the VIA south bridges to the PC machine
> > > > > [1]. It implements missing ACPI functionality which ACPI-aware x86 guests
> > > > > expect for a smooth experience. The implementation is heavily inspired by PIIX4.
> > > >
> > > > I think first the interrupt routing should be fixed because that may change a 
> > > > few things in this series so that should be the next step and then rebase this 
> > > > series on top of that.
> > > >
> > > > What I mean by fixing interrupt routing? You may remember this discussion:
> > > >
> > > > https://patchew.org/QEMU/cover.1677004414.git.balaton@eik.bme.hu/
> > > >
> > > > With pegasos2 your (over)simplification worked only because the firmware of 
> > > > that machine maps everythnig to one ISA IRQ and guests were happy with that. I 
> > > > told you that back then but could not convince you and Mark about that. Now 
> > > > with the amigaone machine the firmware maps VIA devices and PCI interuupt pins 
> > > > to different ISA IRQs so we need to go back either to my otiginal 
> > > > implementation or something else you come up with. You can test this trying to 
> > > > use USB devices with amigaone machine which only works after reverting 
> > > > 4e5a20b6da9b1 and 422a6e8075752. So please either propose something to fix that 
> > > > first or wait with this series until I can update my pathches to solve 
> > > > interrupt routing. I think this series should wait until after that because it 
> > > > adds more interrupt handling which should follow whatever way we come up with 
> > > > for that so it's too early fir this series yet. (If you want to try fixing it 
> > > > keep in mind that in both amigaone and pegasos2 the PCI buses are in the north 
> > > > br
id
> > ge not in the VIA south bridge so don't try to force the IRQ mapping into the 
> > PCI bus. All the VIA chip needs to do is mapping its PIRQ/PINT pins to ISA IRQs 
> > as the VIA is only handling ISA IRQs and all other pci stuff is handled in the 
> > north bridge. So I think we need a via_set_isa_irq function but we could change 
> > it according to Mark's idea to pass the PCI device and use its function number 
> > to select itq source instead of the enum I had in my original series.)
> > > > I have some other comments that I'll add in reply to individual patches for the 
> > > > future/
> > >
> > > Hi Zoltan,
> > >
> > > The interrupt handling introduced in this series is not related to PCI 
> > > interrupt routing: The SMI is a dedicated pin on the device and the SCI is 
> > > mapped internally to an ISA interrupt (note how the power management function 
> > > lacks the registers for PCI interrupt information). Hence, PCI interrupt 
> > > routing isn't changed in this series and therefore seems off-topic to me.
> > >
> > > Moreover, the SMI is a new interrupt which is therefore not used in any machine 
> > > yet. The SCI is deactivated if set to IRQ 0 which is the default even. If a 
> > > guest configures it, it shall be aware to receive an *ISA* interrupt.
> > >
> > > So I think this series shouldn't conflict with any previous work and should not 
> > > be blocked by the PCI IRQ routing topic.
> >
> > The topic I've raised is not about routing PCI interrupts but routing different 
> > IRQ sources in VIA chip (such as different functions plus the PIRQ/PINT pins) 
> > to ISA interrupts so that would conflict with how the PM func interrupts are 
> > routed. I think only the isa function should have qemu_irqs and it should 
> > handle mapping of the different sources to the appropriate ISA IRQ so the 
> > different sources (functions) should not have their own qemu_irqs or gpios but 
> > they would just call via_isa_set_irq with their PCIDevice, pun and level and 
> > then the isa model would do the routing. I plan to do this eventually but it 
> > you're adding more things that would need to be reverted then it becomes more 
> > difficult.
>
> We've had lenghty discussions about this topic before and we -- together 
> -- ended up with the current solution.

Which does not work as demonstrated by the amigaone machine now. I've told 
you that before but you did not accept my arguments so for the sake of 
being able to merge pegasos2 in time for release I've accepted your 
alternative that was still OK for pegasos2 and let this be fixed later 
when we need it. That is about now that we have the amigaone machine. The 
amigaone still boots and usable without fixing this IRQ mapping but some 
devices like USB does not work due to not getting the expected interrupt 
correctly. But if you want to change the via device further I'd like to 
fix it before that to avoid having to rewrtite what you add now.

> This series adds the last missing 
> feature to the VIA south bridges before they can be integrated into the 
> PC machine. Delaying progress by reopening the same topics over and over 
> again really seems unfair to me. Instead, let's be optimistic that we'll 
> end up with a solution that suits all needs well.

I'm sorry if it seems unfair to you but I did not bring this up tp delay 
your work but to avoid more work in the future and fix something that is 
broken to improve the device model. If you PC machine wants to map 
internal functions to different IRQs then you will also get this problem 
so it will need to be fixed and fixing it will also simplify your ACPI 
patches. To help with this I've spent some time now to do the fix I think 
would work so you could just rebase your series on top of that.

> That said, I've ran both the pegasos2.rom and the u-boot.bin for 
> amigaone that is used in the Avocado test. I've traced both with '-trace 
> "pci_cfg_*"'. The result is that neither BIOS pokes the SCI routing 
> register in the ISA function which means that the interrupt stays 
> deactivated. Hence, it is very unlikely that the changes introduced in 
> this series would interfer with guests on these machines.

It does not interfere with guests, it inteferes with fixing probelms with 
interrupt routing that amigaone (and liekly your PC machine) has so it 
makes sense to fix that first because it changes the way SMI should be 
added.

> In summary, I don't see any blockers so far for merging this series for 
> the upcoming release.

I hope I could explain above.

Regards,
BALATON Zoltan