linux-kernel - Re: [PATCH 1/2] PCI: make pci_claim_resource() work with conflict resources as appropriate

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Message-ID: <CAErSpo5hZGAzc17GApEfuzduvzh6haVLBKRvizcRxGLnh8ebuA@mail.gmail.com>
Date:	Thu, 28 Jul 2011 09:59:03 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Deng-Cheng Zhu <dengcheng.zhu@...il.com>
Cc:	jbarnes@...tuousgeek.org, torvalds@...ux-foundation.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mips@...ux-mips.org, eyal@...s.com, zenon@...s.com,
	Ralf Baechle <ralph@...ux-mips.org>
Subject: Re: [PATCH 1/2] PCI: make pci_claim_resource() work with conflict
 resources as appropriate

On Thu, Jul 28, 2011 at 5:28 AM, Deng-Cheng Zhu <dengcheng.zhu@...il.com> wrote:
> In resolving a network driver issue with the MIPS Malta platform, the root
> cause was traced into pci_claim_resource():
>
> MIPS System Controller's PCI I/O resources stay in 0x1000-0xffffff. When
> PCI quirks start claiming resources using request_resource_conflict(),
> collisions happen and -EBUSY is returned, thereby rendering the onboard AMD
> PCnet32 NIC unaware of quirks' region and preventing the NIC from functioning.
> For PCI quirks, PIIX4 ACPI is expected to claim 0x1000-0x103f, and PIIX4 SMB to
> claim 0x1100-0x110f, both of which fall into the MSC I/O range. Certainly, we
> can increase the start point of this range in arch/mips/mti-malta/malta-pci.c to
> avoid the collisions. But a fix in here looks more justified, though it seems to
> have a wider impact. Using insert_xxx as opposed to request_xxx will register
> PCI quirks' resources as children of MSC I/O and return OK, instead of seeing
> collisions which are actually resolvable.

What's the collision?  Can we see the dmesg log (which should have
that information) and maybe the /proc/ioports contents?  Did something
change the order in which we claim resources, so things that used to
work now cause conflicts?

I think insert_resource() (where the newly-inserted resource can
become the parent of something that was previously inserted) is sort
of a hack, and the fact that we need it is telling us that we're doing
things in the wrong order.  It's nicer when we can discover and claim
resources in a top-down hierarchical way.  But I recognize that may
not always be possible, or at least not convenient.

Bjorn
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