Re: [PATCH][RFC v3] PCI: Workaround to enable poweroff on Mac Pro 11

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Sep 05, 2016 at 12:01:21PM +0800, Chen Yu wrote:
> On Fri, Sep 02, 2016 at 11:25:27AM -0500, Bjorn Helgaas wrote:
> > On Wed, Aug 24, 2016 at 04:17:31PM +0200, Lukas Wunner wrote:
> > > On Fri, Aug 19, 2016 at 04:30:25PM +0800, Chen Yu wrote:
> > > > People reported that they can not do a poweroff nor a
> > > > suspend to ram on their Mac Pro 11. After some investigations
> > > > it was found that, once the PCI bridge 0000:00:1c.0 reassigns its
> > > > mm windows to ([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 ram(S3) works.
> > > 
> > > To provide a bit more context:
> > > 
> > > The root port in question (0000:00:1c.0) is not listed in the DSDT.
> > > On macOS, only devices present in the ACPI namespace are incorporated
> > > into the I/O Kit registry. Consequently macOS pretends that this root
> > > port doesn't exist. It's not listed in the "ioreg -l" output and thus
> > > no driver is attached to this device.
> > > 
> > > So what we're dealing with is sloppiness on the part of Apple:
> > > Some engineer probably forgot to disable this unused root port
> > > and they didn't notice it during testing because their OS ignores
> > > such devices.
> > > 
> > > We could in principle achieve the same behaviour by adding a PCI
> > > device only if it has an ACPI companion, perhaps quirk this only
> > > to Macs. I'm not sure if that's the right thing to do though.
> > > What if they hide devices from macOS but we want to access them
> > > on Linux?
> > > 
> > > What's really odd is that changing *memory* windows affects
> > > accessibility of *I/O ports*.
> > > 
> > > One theory would be that I/O ports are somehow mapped into memory.
> > > The GPIO pins of Intel chipsets are usually accessible through
> > > I/O ports, but I've recently looked at the DSDT of the newest
> > > MacBook9,1 (2016) and it looks like they're now accessed through
> > > SystemMemory instead of SystemIO. Perhaps someone at Intel knows
> > > about these intricacies of their chipsets.
> > 
> > Hey, look, Chen Yu works at Intel :)
> >
> Ah yes, please give me some time and I'll try to search for related info
> and give feeback later.

Any news on this?  I was really hoping to make some progress on
this for v4.9, but time is running out.

Bjorn