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

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Message-ID: <CAErSpo6SLCLxh6vOwLaj5AYXNLrUEtQgfMU_hFCKJVH1dC5neQ@mail.gmail.com>
Date:	Fri, 29 Jul 2011 11:35:51 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Deng-Cheng Zhu <dengcheng.zhu@...il.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>, 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
Subject: Re: [PATCH 1/2] PCI: make pci_claim_resource() work with conflict
 resources as appropriate

On Fri, Jul 29, 2011 at 12:32 AM, Deng-Cheng Zhu
<dengcheng.zhu@...il.com> wrote:
> I noticed that at 79896cf42f Linus changed the function from insert_resource()
> to request_resource() (and later evolved into request_resource_conflict()) and
> he explained the reason. So, in the NIC's case, the problem is that in
> pci_claim_resource() the function pci_find_parent_resource() returns the root
> (0x0-0xffffff) rather than the MSC PCI I/O (0x1000-0xffffff).

This seems like the real problem: PCI has the wrong idea of the
resources available on bus 00.  The pci_bus->resource[0] for bus 00
points to ioport_resource (the default put there by pci_create_bus()),
when it should point to to msc_io_resource instead.

Some architectures fill in the pci_bus->resource[] array directly for
host bridges (for examples, try 'grep -r "resource\[0\] = " arch/').
On x86 and ia64, we use pci_bus_remove_resources() and
pci_bus_add_resource(), and I'd prefer that style for new code because
it hides some ugly implementation details.

I'm a little puzzled that we don't see this problem on more
architectures.  The grep above only found a few arches that update the
root bus resources.  I would expect most of the ones it didn't find to
be broken the same way Malta is.

Bjorn
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