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Re: [Qemu-ppc] [Qemu-devel] [PATCH] sam460ex: Fix PCI interrupt connecti

From: David Gibson
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH] sam460ex: Fix PCI interrupt connections
Date: Tue, 31 Jul 2018 16:06:17 +1000
User-agent: Mutt/1.10.0 (2018-05-17)

On Tue, Jul 31, 2018 at 06:57:31AM +0200, Sebastian Bauer wrote:
> Am 2018-07-31 02:18, schrieb David Gibson:
> > > David, can you please drop this patch, we'll come up with a
> > > different fix.
> > Done.  Should have looked at that patch a bit closer.
> I created a follow up patch, unfortunately, based on the previous patch, as
> I did not spot your mail earlier than now. Note that the previous patch was
> an improvement over the old behaviour and under normal conditions the
> difference was not visible (as the OS serves both interrupts in the same run
> and at least on AmigaOS the interrupt handling is deferred but IRQs are
> acked quickly; it is still not correct though). The old implementation was
> not correct at all, i.e., all interrupts were missed. So it was technical an
> improvement (and the easiest to come up without deep understanding QEMU) ;)
> Anyway, I don't know if that follow up patch is the right approach. But
> building the logical or gate seems also be very much code, especially as in
> pci.c the case of multiple irqs sources are seems to be already handled (if
> I understand that code correctly). The follow up patch most likely does not
> model the hardware correctly, but the behaviour should be the same. The
> logical or gate would model the hardware more closely.

Yeah, I think routing all the irqs to pin A should be ok for now.
AIUI it's not user or guest visible so we can fix it up later if we
get more information on the hardware.  I believe there are a number of
other embedded boards that have a similar hack too, since they only
have a single PCI LSI line on the board-level PIC.

> Let me know if I should rebase to the state before my initial patch (I just
> looked and the previous patch was still not dropped) if you think that the
> change is fine.

I'd prefer a rebase onto the current state of my ppc-for-3.0 tree,

> There is also the possibility to make the special (num-irqs == 1) the common
> case, as the Sam460ex platform is the only user of this bus so far (and
> probably stays the only one). I'm not sure if it is worth all the hassle.
> Also note that the entire ppc440_pcix.c source file seems to be created for
> the sam board. I have no idea why that mapping function based on slots was
> chosen in the first place so I kept it. I would also be fine to remove that,
> which would simplify things a lot.
> Let me know how to proceed.
> Bye
> Sebastian

David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!

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