From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] PCI: Fix pcibios_update_irq misuse of irq number
Date: Tue, 03 Feb 2015 11:37:30 +0000 [thread overview]
Message-ID: <54D0B2FA.9080600@arm.com> (raw)
In-Reply-To: <4324891.mqG6Yyfi6J@wuerfel>
On 03/02/15 11:31, Arnd Bergmann wrote:
> On Tuesday 03 February 2015 10:38:25 Marc Zyngier wrote:
>>
>> That's exactly what I thought until Lorenzo reported kvmtool falling
>> over because of this write. Obviously, some platforms must actually
>> require this (possibly for bridges that are not known by the firmware).
>
> This sounds much like a bug in kvmtool.
Lorenzo and I just came to a similar conclusion, given that the HW
should never use that information.
>> Entirely removing that code solves my problem too, but that'd cannot be
>> the right solution...
>
> The comment in pdev_fixup_irq() says
>
> /* Always tell the device, so the driver knows what is
> the real IRQ to use; the device does not use it. */
>
> which I read to mean that there are drivers that incorrectly use
> 'pci_read_config_byte(dev, PCI_INTERRUPT_LINE)' as the number
> they pass into request_irq, rather than using dev->irq.
> However, this means that your patch is actually wrong, because
> what the driver cares about is the virtual irq number (which
> request_irq expects), not the number relative to some interrupt
> controller.
Yes, I now realise that. That makes a lot more sense actually, because I
was getting very confused about how the HW should interpret that number.
Side question: In the probe-only case, should we still allow this write
to happen?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2015-02-03 11:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-28 14:51 [PATCH] PCI: Fix pcibios_update_irq misuse of irq number Marc Zyngier
2015-01-28 15:21 ` Jiang Liu
2015-01-28 15:27 ` Marc Zyngier
2015-01-28 15:43 ` Bjorn Helgaas
2015-02-02 16:15 ` Marc Zyngier
2015-02-02 16:22 ` Bjorn Helgaas
2015-02-02 15:57 ` Bjorn Helgaas
2015-02-02 16:06 ` Jiang Liu
2015-02-02 16:23 ` Marc Zyngier
2015-02-02 16:33 ` Russell King - ARM Linux
2015-02-02 18:08 ` Marc Zyngier
2015-02-02 18:20 ` Russell King - ARM Linux
2015-02-02 17:02 ` Arnd Bergmann
2015-02-03 10:38 ` Marc Zyngier
2015-02-03 11:31 ` Arnd Bergmann
2015-02-03 11:37 ` Marc Zyngier [this message]
2015-02-03 12:57 ` Arnd Bergmann
2015-02-04 15:39 ` [PATCH] kvmtool: don't use PCI config space IRQ line field Andre Przywara
2015-02-06 18:55 ` Will Deacon
2015-02-06 19:02 ` Peter Maydell
2015-02-06 19:07 ` Will Deacon
2015-02-07 21:24 ` arnd at arndb.de
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