linux-kernel - Re: [PATCH] PCI: Remove not needed check in disable aspm link

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Date:	Wed, 12 Jun 2013 12:41:42 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	Roman Yepishev <roman.yepishev@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] PCI: Remove not needed check in disable aspm link

On Wed, Jun 12, 2013 at 10:05 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>> current code from acpi_pci_root_add we have
>>   1. pci_acpi_scan_root
>>          ==> pci devices enumeration and bus scanning.
>>              ==> pci_alloc_child_bus
>>                  ==> pcibios_add_bus
>>                      ==> acpi_pci_add_bus
>>                          ==> acpiphp_enumerate_slots
>>                              ==> ...==> register_slot
>>                                   ==> device_is_managed_by_native_pciehp
>>                                         ==> check osc_set with
>> OSC_PCI_EXPRESS_NATIVE_HP_CONTROL
>>    2. _OSC set request
>>
>> so we always have acpiphp hotplug slot registered at first.
>>
>> so either we need to
>> A. revert reverting about _OSC
>> B. move pcibios_add_bus down to pci_bus_add_devices()
>>     as acpiphp and apci pci slot driver are some kind of drivers for pci_bus
>> C. A+B
>
> It doesn't surprise me at all that there are problems in the _OSC code
> and the acpiphp/pciehp interaction.  That whole area is a complete
> disaster.  It'd really be nice if somebody stepped up and reworked it
> so it makes sense.
>
> But this report is useless to me.  I don't have time to work out what
> the problem is and how it affects users and come up with a fix.

effects: without fix the problem, user can not use pcie native hotplug
if their system's firmware support acpihp and pciehp.
And make it worse, that acpiphp have to be built-in, so they have no
way to blacklist acpiphp in config.

>
> My advice is to simplify the path first, and worry about fixing the
> bug afterwards.  We've already done several iterations of fiddling
> with things, and I think all we're doing is playing "whack-a-mole" and
> pushing the bugs around from one place to another.

We need to address regression at first.
my suggestion is : revert the reverting and apply my -v3 version that will fix
regression that Roman Yepishev met.

please check attached two patches, hope it could save your some time.

Yinghai

Download attachment "revert_revert_osc_change_linus.patch" of type "application/octet-stream" (5303 bytes)

Download attachment "disable_aspm_3_linus.patch" of type "application/octet-stream" (8145 bytes)