linux-kernel - Re: [PATCH] pci: check PCI_EXP_FLAGS_SLOT before setting hotplug bridge

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Date:	Tue, 19 Nov 2013 13:57:14 +0800
From:	Adam Lee <adam.lee@...onical.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Amos Kong <kongjianjun@...il.com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Thomas Renninger <trenn@...e.de>,
	Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH] pci: check PCI_EXP_FLAGS_SLOT before setting hotplug
 bridge

On Mon, Nov 18, 2013 at 10:38:17AM -0700, Bjorn Helgaas wrote:
> [+cc Myron, Amos, Thomas, Ben]
> 
> On Mon, Nov 18, 2013 at 2:40 AM, Adam Lee <adam.lee@...onical.com> wrote:
> > This patch adds the PCI_EXP_FLAGS_SLOT check back before setting
> > hotplug bridge, which is omitted by an API switching commit,
> > 59875ae489609b2267548dc85160c5f0f0c6f9d4 "PCI/core: Use PCI Express
> > Capability accessors".
> >
> > Some Lenovo laptops hang in booting without this fix.
> 
> What kernel version hangs?  I suspect you might be missing 6d3a1741f1
> ("PCI: Support PCIe Capability Slot registers only for ports with
> slots"), because it *looks* like the current kernel should work
> correctly even without your patch.

No, patching 6d3a1741f1 and d3694d4fa3 doesn't fix the hang.

It hangs in acpi_evaluate_integer() from
59875ae489609b2267548dc85160c5f0f0c6f9d4 "PCI/core: Use PCI Express
Capability accessors" and before
ac212b6980d8d5eda705864fc5a8ecddc6d6eacc "ACPI / processor: Use common
hotplug infrastructure", 3.4~3.11. (double confirmed)

I didn't mention this because:
1, that check is omitted obviously, an API switching patch should not
remove things like that.
2, have run some tests, adding the check back is harmless.
3, I believe ac212b6 just workarounds the hang unexpectedly, bug still
exists.

-- 
Adam Lee
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