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Re: [PATCH 4/5] hw/ppc/ppc4xx_pci: Replace pointless warning by assert()

From: Peter Maydell
Subject: Re: [PATCH 4/5] hw/ppc/ppc4xx_pci: Replace pointless warning by assert()
Date: Mon, 11 Jan 2021 17:41:54 +0000

On Mon, 11 Jan 2021 at 01:11, Nathan Chancellor
<natechancellor@gmail.com> wrote:
> On Tue, Sep 01, 2020 at 12:40:42PM +0200, Philippe Mathieu-Daudé wrote:
> > We call pci_register_root_bus() to register 4 IRQs with the
> > ppc4xx_pci_set_irq() handler. As it can only be called with
> > values in the [0-4[ range, replace the pointless warning by
> > an assert().
> >
> > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> Hopefully reporting this here is okay, I find Launchpad hard to use but
> I can file it there if need be.
> The assertion added by this patch triggers while trying to boot a
> ppc44x_defconfig Linux kernel:

This is the same issue reported here by Guenter:
It's still there in master (you can see it if you apply my fix
to get past the earlier kernel panic).

The QEMU code as it stands for the Bamboo PCI interrupts is clearly
wrong. The problem is that I don't know what the hardware's
actual behaviour is, so it's hard to fix the model...
A comment in hw/ppc/ppc4xx_pci.c claims
"On Bamboo, all pins from each slot are tied to a single board IRQ."
Code in hw/ppc/ppc440_bamboo.c wires four irq lines from the
PCI controller up to UIC lines 25, 26, 27, 28.

Does anybody have documentation for this board ? What is Linux
expecting the PCI IRQ wiring to be (not necessarily an indication
that that's what the h/w does, but a useful clue :-)) ?

-- PMM

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