linux-kernel - Re: [PATCH] pci/hotplug: work-around for missing

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Date:	Mon, 18 May 2015 10:33:08 -0400
From:	Jarod Wilson <jarod@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci/hotplug: work-around for missing _RMV on HP ZBook
 G2

On 5/17/2015 8:26 PM, Rafael J. Wysocki wrote:
> On Saturday, May 16, 2015 09:41:55 AM Bjorn Helgaas wrote:
>> On Sat, May 16, 2015 at 09:37:50AM -0500, Bjorn Helgaas wrote:
>>> Hi Jarod,
>>>
>>> On Thu, May 14, 2015 at 03:33:58PM -0400, Jarod Wilson wrote:
>>>> The HP ZBook 15 and 17 Mobile Workstations, generation 2, up to and
>>>> including at least BIOS revision 01.07, do not have an ACPI _RMV object
>>>> associated with their expresscard slots, so acpi-based hotplug-capable
>>>> slot detection fails. If we fall back to pcie-based detection, the systems
>>>> work just fine, so this uses dmi matching to do that. With luck, a future
>>>> BIOS will remedy this (I've let someone at HP know about the problem),
>>>> but for now, just use this for all existing versions.
...
>>> Oh, my goodness.  I forgot how terrible this path is.  Can anyone write a
>>> simple explanation of how we choose to use acpiphp or pciehp?
>
> In theory, that should depend on the _OSC handshake in acpi_pci_root_add().
>
> If the firmware doesn't give us control of the PCIe features, we'll not use
> pciehp (or at least that's the idea).
>
> acpiphp is used if pciehp doesn't claim the device, AFAICS.

[    4.013326] acpi PNP0A08:00: _OSC: OS supports [ExtendedConfig ASPM 
ClockPM Segments MSI]
[    4.015860] acpi PNP0A08:00: _OSC: OS now controls [PCIeHotplug PME 
AER PCIeCapability]

So at a glance, it would appear that pciehp *should* be claiming it, 
right? Something I noted in the bug I filed is that the device ID 
reported there is PNP0A08, and the root_device_id table that associates 
with acpi_pci_root_add() only includes PNP0A03 in it. Is that correct, 
or should 08 also be in there, which might remedy this? (I can test this 
out easily enough).

-- 
Jarod Wilson
jarod@...hat.com
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