linux-kernel - Re: [Bug 41722] Clevo M5X0JE hangs in ACPI init

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Message-ID: <CA+55aFxmj_+0eLYqKZb6qWb_Zc4E4R8WrmbsVgv5BbNwvnqouQ@mail.gmail.com>
Date:	Sun, 8 Jan 2012 14:23:29 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Rogério Brito <rbrito@....usp.br>
Cc:	bugzilla-daemon@...zilla.kernel.org,
	Edward Donovan <edward.donovan@...ble.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-kernel@...r.kernel.org,
	Márcia Coutinho de Brito <mcbrito@...il.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>, Ram Pai <linuxram@...ibm.com>
Subject: Re: [Bug 41722] Clevo M5X0JE hangs in ACPI init

On Sun, Jan 8, 2012 at 2:13 PM, Rogério Brito <rbrito@....usp.br> wrote:
>
> It doesn't boot with a vanilla kernel. It only boots when I pass the options
> above *and* compile the kernel with the following patch applied:
>
> ,----[ do_not_size_subtractive_decoding_transparent_pci_to_pci_bridges.patch ]
> | diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> | index 86b69f85..84543f5 100644
> | --- a/drivers/pci/setup-bus.c
> | +++ b/drivers/pci/setup-bus.c
> | @@ -849,6 +849,10 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus,
> |               break;
> |
> |       case PCI_CLASS_BRIDGE_PCI:
> | +             /* don't size subtractive decoding (transparent)
> | +              * PCI-to-PCI bridges */
> | +             if (bus->self->transparent)
> | +                     break;
> |               pci_bridge_check_ranges(bus);
> |               if (bus->self->is_hotplug_bridge) {
> |                       additional_io_size  = pci_hotplug_io_size;
> `----

Ahh. I'd forgotten about that particular PCI patch.

That is definitely the right thing to do, and commit 8fa5913d54f3
("PCI: remove transparent bridge sizing") did exactly that, but then
we reverted it in commit 12c22d6ef299 because it caused some odd
problems for some people.

I think we should try to re-do that "avoid sizing transparent bridges"
commit, because it really should make it much easier to do PCI
allocations under some very common situations (there's a *lot* of
common intel transparent PCI bridges).

Jesse, Yinghai, Ram - should we try to just re-do that commit in this
merge window, and see how that goes? We can always revert it again if
it causes problems..

                         Linus
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