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Date:	Sun, 17 Jan 2010 14:35:35 -0800
From:	Yinghai Lu <>
To:	Jesse Barnes <>
CC:	Bjorn Helgaas <>, Alex Chiang <>,
	Ingo Molnar <>,
	Linus Torvalds <>,
	Ivan Kokshaysky <>,
	Kenji Kaneshige <>,,
Subject: Re: [PATCH 10/11] pciehp: add support for bridge resource reallocation

On 01/17/2010 09:34 AM, Jesse Barnes wrote:
> On Sat, 16 Jan 2010 16:14:31 -0700
> Bjorn Helgaas <> wrote:
>> On Sat, 2010-01-16 at 01:34 -0800, Yinghai Lu wrote:
>>> On 01/15/2010 08:59 PM, Alex Chiang wrote:
>>>> * Yinghai Lu <>:
>>>>> From: Kenji Kaneshige <>
>>>>> With this patch, pciehp driver try to clear PCI bridge resources
>>>>> to parent bridge (root port or switch downstream port) of the
>>>>> slot
>>>>> so we can shrink pci bridge resource for those port
>>>>> This feature is enabled when 'pciehp_realloc' option is
>>>>> specified.
>>>>> -v2: make it could be appiled after Yinghai patchset that touch
>>>>> pci bridge resource also remove poweron check, because
>>>>> pci_bridge_release_res will check child at first
>>>> Same comment as my earlier patch. Why not just make this the
>>>> default behavior, instead of introducing yet another command line
>>>> parameter for users to guess at?
>>> it will break Eric's setup/
>> I think this is a clue that we don't understand the problem well
>> enough yet.
>> I'm opposed to adding kernel parameters for this sort of thing.  It is
>> unreasonable to expect users to figure out whether they need to use
>> this parameter or not.
>> Special-case switches like this make it much harder to maintain the
>> code in the future.
> Agreed.  Yinghai, what's wrong in the new reassignment code that
> causes Eric's setup to break?  Can we just fix that instead and enable
> reallocation by default?


Eric's setup is:
hot plug one addon card into one hotplug slots and new addon cards have more hot plug slots.

SLOTA will have SLOT B, SLOT C, and SLOT D as children. and not devices in SLOTB/C/D at first.

with the pciehp_realloc is specified, the SLOTA will not get any device assigned, and later
if put devices in SLOTB/SLOTC/SLOTD, will not get resource for those devices.
and we can not go above to update SLOT A, because: some devices on SLOTB could already have driver loaded.

if you don't like pciehp_realloc at this point, please only apply 1-8 and 11.


Yinghai Lu
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