linux-kernel - Re: [PATCH v3 3/6] ACPI/pci_slot: update PCI slot information when PCI hotplug event happens

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Date:	Thu, 10 Jan 2013 15:40:45 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Myron Stowe <mstowe@...hat.com>, Jiang Liu <liuj97@...il.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Yijing Wang <wangyijing@...wei.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Myron Stowe <myron.stowe@...hat.com>,
	bhelgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v3 3/6] ACPI/pci_slot: update PCI slot information when
 PCI hotplug event happens

On Thu, Jan 10, 2013 at 3:39 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Thursday, January 10, 2013 03:03:53 PM Yinghai Lu wrote:
>> On Thu, Jan 10, 2013 at 1:50 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> > Well, I don't see what functional problems that can bring.
>> >
>> > In theory people may want to have them as modules to avoid loading them on
>> > systems that don't use PCI hotplug, but honestly I think that the complexity
>> > this causes us to deal with is not worth it.
>> >
>> > Moreover, removing the modularity may actually allow us to solve some ordering
>> > issues once and for good.
>>
>> No, the world is not really ideal yet.
>>
>> looks like laptops have problem with pci express cards.
>>
>> when pciehp is used, surprise insert/removal does not work because
>> PresDect does not change properly, so no interrupt is generated.
>> --- i suspects that is silicon problem.
>>
>> but when acpiphp is used, that surprise  insert/removal is working.
>>
>> some laptop like thinkpad, just don't give osc to kernel..
>> [    0.505117]  pci0000:00: Requesting ACPI _OSC control (0x1d)
>> [    0.505413]  pci0000:00: ACPI _OSC request failed (AE_SUPPORT),
>> returned control mask: 0x0d
>> [    0.505517] ACPI _OSC control for PCIe not granted, disabling ASPM
>>
>> and other laptop give that to kernel, in recent kernel will not give
>> acpiphp to have that slot, because it want to hold that for pciehp.
>> poor user have to pass 'pci_aspm=off" to disable _OSC for all.
>> --- please check the mail that i forward to you yesterday.
>
> Yes, this is a bug, but I'm not sure how to fix it yet.

add one command line to control it so do not claim that in osc_control?

>
>> Anyway, we do need to let the user to have choice to use acpiphp and pciehp.
>> and it should be first come and first serve policy.
>
> And that's why you think they should be modules?  I disagree if so.

Yes.

maybe we can have pci=nopciehp in command line just we pci=noaer...

that should handle some corner cases.
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