linux-kernel - Re: post 2.6.26 requires pciehp_slot_with

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Message-ID: <488FD59B.4080302@jp.fujitsu.com>
Date:	Wed, 30 Jul 2008 11:44:43 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	Pierre Ossman <drzeus-list@...eus.cx>,
	Alex Chiang <achiang@...com>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	Kristen Accardi <kristen.c.accardi@...el.com>
Subject: Re: post 2.6.26 requires pciehp_slot_with_bus

Jesse Barnes wrote:
> On Monday, July 28, 2008 7:43 pm Kenji Kaneshige wrote:
>>> Your systems don't have _RMV methods for the hotpluggable PCIe slots in
>>> the DSDT?  That's a shame; the Windows docs I found on PCIe hotplug
>>> seemed to indicate that _RMV and _OSC (under Vista) were used to detect
>>> whether a given slot was hot pluggable (I just googled for "windows pcie
>>> hotplug" or something) so I was hoping that would be a reliable method...
>>>  Any other ideas?  I'll go see if I can dig up some ExpressCard info.
>> My systems don't have _RMV methods for the hot pluggable PCIe slots in the
>> DSDT, but I don't think that's a shame. I suppose that the document you are
>> referring describes how Windows handles ExpressCard slots. In my
>> understanding, Hot Plug Surprise bit in the Slot Capabilities register is
>> set to 1b on ExpressCard slots, and I believe that ACPI _RVM method is for
>> the device that only supports surprise-style removal. I think this is why
>> your system implements _RMV method for slots.
> 
> Yeah, that may be.  The document wasn't very clear; I was hoping that 
> something simple would be available.
> 
>> On the other hand, hot pluggable slots on my servers are *not* ExpressCard
>> slots, and all of them have Power Controller instead of surprise-style
>> removal (Hot Plug Surprise bit in the Slot Capabilities register is set to
>> 0b). So I believe there is no reason to implement _RMV methods for the hot
>> pluggable PCIe slots on my systems.
>>
>> Here is an idea. How about using _RMV method to determine whether a given
>> slot is actually hot pluggable when Hot Plug Surprise bit in the Slot
>> Capabilities register is set to 1b on the slot? This is based on a little
>> rough assumption that all PCIe slots that support surprise-style removal
>> have _RMV method, though. Does this work for you?
> 
> It's worth a try.  We need *some* sort of better method to detect hot 
> pluggable slots...

OK. I'll try to make a patch.

According to PCI Express and PCI firmware spec, I think Hot Plug Capable
bit in the Slot Capabilities register and ACPI _OSC are enough to detect
hot pluggable slots. But I might be missing something especially about
ExpressCard, or BIOS is just broken...

Thanks,
Kenji Kaneshige


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