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

From: Yinghai Lu
Date: Wed Jun 12 2013 - 15:41:50 EST

On Wed, Jun 12, 2013 at 10:05 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> 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
>> 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.


Attachment: revert_revert_osc_change_linus.patch
Description: Binary data

Attachment: disable_aspm_3_linus.patch
Description: Binary data