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

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jun 08, 2016 at 12:31:27PM +0800, Chen Yu wrote:
> Hi Bjorn,
> 
> On 2016年05月31日 21:16, Bjorn Helgaas wrote:
> >On Tue, May 31, 2016 at 03:18:02PM +0800, Chen Yu wrote:
> >>On 2016年05月31日 15:00, Yinghai Lu wrote:
> >>>On Mon, May 30, 2016 at 8:24 PM, Chen Yu <yu.c.chen@intel.com> wrote:
> >>>
> >>>>and then in pcibios_assign_resources, 0000:00:1c.0 tries to allocate minimal
> >>>>resource window and then update related base/limit registers:
> >>>>
> >>>>[    0.865342] pci 0000:00:1c.0: bridge window [io  0x1000-0x0fff] to [bus
> >>>>02] add_size 1000
> >>>>[    0.865343] pci 0000:00:1c.0: bridge window [mem 0x00100000-0x000fffff
> >>>>64bit pref] to [bus 02] add_size 200000 add_align 100000
> >>>>[    0.865344] pci 0000:00:1c.0: bridge window [mem 0x00100000-0x000fffff]
> >>>>to [bus 02] add_size 200000 add_align 100000
> >>>>
> >>>That is for hotplug bridge, then we could use following instead.
> >>>
> >>>diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> >>>index ee72ebe..d3ec833 100644
> >>>--- a/drivers/pci/quirks.c
> >>>+++ b/drivers/pci/quirks.c
> >>>@@ -2775,6 +2775,13 @@ static void quirk_hotplug_bridge(struct pci_dev *dev)
> >>>
> >>>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HINT, 0x0020, quirk_hotplug_bridge);
> >>>
> >>>+static void quirk_hotplug_bridge_skip(struct pci_dev *dev)
> >>>+{
> >>>+       dev->is_hotplug_bridge = 0;
> >>>+}
> >>>+
> >>>+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x8c10,
> >>>quirk_hotplug_bridge_skip);
> >>>+
> >>>  /*
> >>>   * This is a quirk for the Ricoh MMC controller found as a part of
> >>>   * some mulifunction chips.
> >>Good idea, but in this way we might not have io window allocated for
> >>it?I'm not sure
> >>if this would break wifi,etc, I'll suggest reporters to have a try.
> >Let's figure out the root cause before trying more random fixes.  I
> >have the same objection to the patch above.  No doubt there are many
> >ways we could "fix" this, but unless we know the root cause, we're
> >likely to make a change that's not a complete fix or will cause other
> >issues in the future.
> >
> I just let the reporter  paste their lspci in Mac OS, it looks that
> Mac OS also
> does not allocate any resource for this broken pci bridge, and other pci
> devices have almost the same resource region as it is in linux, so I think
> this is an evidence that Apple does not want to use this firmware for now,
> maybe reserved for future use, declaim resource for this pci bridge might
> cause unpredictable result, how about adding a dmi+pci quirk for this
> special platform?

This is not a root cause.  We still have no idea why the problem
occurs.  I do not think a quirk is a good idea until we know what the
problem is and exactly how a quirk would fix it.

> lspci result from Mac OS, there's no resource behind this bridge:
> https://bugzilla.kernel.org/attachment.cgi?id=219321
> 
> 
> thanks,
> Yu