Re: [PATCH][RFC] PCI: Workaround to enable poweroff on Mac Pro 11

[Lukas Wunner <lukas@wunner.de>]

On Mon, May 30, 2016 at 04:33:05PM -0500, Bjorn Helgaas wrote:
> On Mon, May 30, 2016 at 06:33:24PM +0800, Chen Yu wrote:
> > Currently there are many people reported that they can not
> > do a poweroff nor a suspend to memory on their Mac Pro 11.
> > After some investigations it was found that, once the PCI bridge
> > 0000:00:1c.0 reassigns its mm windows([mem 0x7fa00000-0x7fbfffff]
> > and [mem 0x7fc00000-0x7fdfffff 64bit pref]), the region of ACPI
> > io resource 0x1804 becomes unaccessible immediately, where the
> > ACPI Sleep register is located, as a result neither poweroff(S5)
> > nor suspend to memory(S3) works.
> > 
> > I don't know why setting the base/limit of PCI bridge mem resource
> > would affect another io resource region, so this quirk just simply
> > bypass the assignment of these mm resources on 0000:00:1c.0, by
> > resetting the resource flag to 0 before updating the base/limit registers.
> > This patch also introduces a new pci fixup phase before the actual bridge
> > resource assignment.
> 
> Split the new fixup phase into a separate patch.
> 
> I'm doubtful about this because we don't understand the root cause.

Agreed.


> > +}
> > +DECLARE_PCI_FIXUP_ASSIGN(PCI_VENDOR_ID_INTEL, 0x8c10, quirk_mac_disable_mmio_bar);
> 
> Is this device *only* used on the Mac Pro 11?  http://pci-ids.ucs.cz
> says "8 Series/C220 Series Chipset Family PCI Express Root Port #1",
> which sounds pretty generic.

It's a root port of a standard Haswell chipset.

This concerns the Mac*Book*Pro11 (not MacPro11), and apparently only
the two models introduced 2015, MacBookPro11,4 and MacBookPro11,5
(can be queried with DMI). I've never heard of issues like this on the
2013/2014 models (MacBookPro11,1 to 11,3).

Looking at the lspci output of the MacBookPro11,4 I notice that the
root port in question, 00:1c.0, has secondary bus 02 below it, but
there are no devices listed on that bus:
https://bugzilla.kernel.org/attachment.cgi?id=218181

On the MacBookPro11,5, there's bus 03 below that port, but likewise
without any devices:
https://launchpadlibrarian.net/222477783/Lspci.txt

It looks like this root port is unused, so perhaps the best option
is to disable it as if it were an appendix. I.e., don't scan it at all,
put it into D3 and leave it alone.

Best regards,

Lukas