Date:   Fri, 30 Jun 2017 08:24:33 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH][RFC v3] PCI: Workaround to enable poweroff on Mac Pro 11

On Fri, Jun 30, 2017 at 11:06:46AM +0800, Chen Yu wrote:
> Hi Bjorn,
> On Thu, Jun 29, 2017 at 09:39:31PM -0500, Bjorn Helgaas wrote:
> > On Thu, Jun 29, 2017 at 02:19:26PM -0500, Bjorn Helgaas 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.
> > > > 
> > > > As suggested by Bjorn, further testing shows that, there is an
> > > > unreported device may be (using) conflict with above aperture,
> > > > which brings unpredictable result such as the failure of accessing
> > > > the io port, which blocks the poweroff(S5). Besides if we reassign
> > > > the memory aperture to the other place, the poweroff works again.
> > > > 
> > > > As we do not find any resource declared in _CRS which contain above
> > > > memory aperture, and Mac OS does not use this pci bridge neither, we
> > > > choose a simple workaround to clear the hotplug flag(suggested by
> > > > Yinghai Lu), thus do not allocate any resource for this pci bridge,
> > > > and thereby no conflict anymore.
> > > > 
> > > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=103211
> > > > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > > > Cc: Rafael J. Wysocki <rafael@...nel.org>
> > > > Cc: Lukas Wunner <lukas@...ner.de>
> > > > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > > > ---
> > > >  drivers/pci/quirks.c | 20 ++++++++++++++++++++
> > > >  1 file changed, 20 insertions(+)
> > > > 
> > > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > > > index 37ff015..04bbdba 100644
> > > > --- a/drivers/pci/quirks.c
> > > > +++ b/drivers/pci/quirks.c
> > > > @@ -2776,6 +2776,26 @@ static void quirk_hotplug_bridge(struct pci_dev *dev)
> > > >  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HINT, 0x0020, quirk_hotplug_bridge);
> > > >  
> > > >  /*
> > > > + * Apple: Avoid programming the memory/io aperture of 00:1c.0
> > > > + *
> > > > + * BIOS does not declare any resource for 00:1c.0, but with
> > > > + * hotplug flag set, thus the OS allocates:
> > > > + * [mem 0x7fa00000 - 0x7fbfffff]
> > > > + * [mem 0x7fc00000-0x7fdfffff 64bit pref]
> > > > + * which is conflict with an unreported device, which
> > > > + * causes unpredictable result such as accessing io port.
> > > > + * So clear the hotplug flag to work around it.
> > > > + */
> > > > +static void quirk_apple_mbp_poweroff(struct pci_dev *dev)
> > > > +{
> > > > +	if (dmi_match(DMI_PRODUCT_NAME, "MacBookPro11,4") ||
> > > > +	    dmi_match(DMI_PRODUCT_NAME, "MacBookPro11,5"))
> > > > +		dev->is_hotplug_bridge = 0;
> > > > +}
> > > > +
> > > > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x8c10, quirk_apple_mbp_poweroff);
> > > > +
> > > > +/*
> > > >   * This is a quirk for the Ricoh MMC controller found as a part of
> > > 
> > > I give up.  We're not making any progress on this.  I propose the
> > > following patch for v4.13.  This is slightly modified to:
> > > 
> > >   - move to arch/x86/pci/fixups.c, since I think this is specific to
> > >     x86
> > > 
> > >   - only clear dev->is_hotplug_bridge for the 00:1c.0 bridge, since
> > >     these systems contain other bridges where I think we *do* want to
> > >     support hotplug, e.g., the Thunderbolt bridge at 09:00.0 (from
> > >     https://bugzilla.kernel.org/attachment.cgi?id=210611)
> > > 
> > >   - log a note in dmesg about what we're doing
> > > 
> > > commit f7bf6baa11b84534d0b7f5ceee06e3349948c853
> > > Author: Chen Yu <yu.c.chen@...el.com>
> > > Date:   Fri Aug 19 16:30:25 2016 +0800
> > > 
> > >     PCI: Work around poweroff & suspend-to-RAM issue on Macbook Pro 11
> > >     
> > >     Neither soft poweroff (transition to ACPI power state S5) nor
> > >     suspend-to-RAM (transition to state S3) works on the Macbook Pro 11,4 and
> > >     11,5.
> > >     
> > >     The problem is related to assigning the [mem 0x7fa00000-0x7fbfffff] space
> > >     to the 00:1c.0 Root Port.  This port isn't connected to anything, but it
> > >     advertises hotplug support in its PCIe Capability.  Initially it has no
> > >     windows assigned, and if Linux leaves it that way, poweroff and
> > >     suspend-to-RAM work fine.
> > >     
> > >     Since the port supports hotplug, Linux assigns windows for future hot-added
> > >     devices.  We currently assign [mem 0x7fa00000-0x7fbfffff] for the memory
> > >     window, and poweroff and suspend-to-RAM don't work after this assignment.
> > >     
> > >     Linux does a soft poweroff (transition to S5) by writing to PM1_CNT at
> > >     [io 0x1804].  The theory about why this doesn't work is:
> > >     
> > >       - The write to PM1_CNT causes an SMI.
> > >       - The BIOS SMI handler depends on something in [mem 0x7fa00000-0x7fbfffff].
> > >       - When Linux assigns [mem 0x7fa00000-0x7fbfffff] to the 00:1c.0 Port, it
> > >         covers up whatever the SMI handler uses, so the SMI handler no longer
> > >         works correctly.
> > >     
> > >     Mark the 00:1c.0 bridge as not supporting hotplug, so we don't assign the
> > >     [mem 0x7fa00000-0x7fbfffff] space to it.
> > >     
> > >     Note that we don't know what the real conflict is, so other use of this
> > >     memory range by another device may cause similar problems.
> > >     
> > >     Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=103211
> > >     Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > >     [bhelgaas: limit to device 00:1c.0, add printk, changelog, comment]
> > >     Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > >     Cc: Rafael J. Wysocki <rafael@...nel.org>
> > >     Cc: Lukas Wunner <lukas@...ner.de>
> > > 
> > 
> > This patch stinks, sorry.  I'll try again tomorrow.  The problem is
> > the address space, not the device, so we should be able to do better
> > than this.
> It is a quite old bug and thanks for taking care of this :-). Do you mean
> reserve the [mem 0x7fa00000-0x7fbfffff] thus no one could allocate this region?

Yes, exactly.  That seems like a more robust solution.  I can't
remember if we've tried that before or not.  Likely we could narrow
that down to a smaller region; I can't remember if we've done that,
either.

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