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Date: Fri, 23 Aug 2013 22:53:20 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Neil Horman <nhorman@...driver.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
linux-acpi@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>,
Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] ACPI: Fix osc flag setup ordering to allow pcie hotplug use when available
On Friday, August 23, 2013 04:05:11 PM Neil Horman wrote:
> On Fri, Aug 23, 2013 at 09:38:18PM +0200, Rafael J. Wysocki wrote:
> > [CCs added]
> >
> > Please always send PCI-related material to linux-pci in the first place.
> >
> Sorry, I ran get_maintainers and it seemed to think linux-acpi was sufficient.
>
> > The change that broke things for you was actually intentional:
> >
> > commit b8178f130e25c1bdac1c33e0996f1ff6e20ec08e
> > Author: Bjorn Helgaas <bhelgaas@...gle.com>
> > Date: Mon Apr 1 15:47:39 2013 -0600
> >
> > Revert "PCI/ACPI: Request _OSC control before scanning PCI root bus"
> >
> > This reverts commit 8c33f51df406e1a1f7fa4e9b244845b7ebd61fa6.
> >
> > so I think we'll need to clean up the ASMP initialization after all.
> >
> Crud. Reading over the revert commit, it seems like the problem boils down to
> the odering of checking aspm_disabled. It seems to me that the simple fix is to
> track the desire for acpi to disable aspm separately from the users desire to
> disable aspm (aspm_disabled). Then we just turn the points where we check the
> aspm_disabled into the appropriate or of two variables, except for
> pcie_asmp_sanity_check, which remains sensitive to just the user disable option.
>
> Or is there more to this?
No, I think you're right.
Bjorn, what do you think?
Rafael
> > On Friday, August 23, 2013 01:19:39 PM Neil Horman wrote:
> > > Somewhere between 3.9 and 3.10 it seems the order in which pcie and acpi probed
> > > slots for hotplug capabilites got reversed. While this isn't a big deal, it did
> > > uncover a bug in the ACPI bus setup path. Specifically, acpi_pci_root_add calls
> > > pci_acpi_scan_root before setting the osc flags for the device handle.
> > > pci_acpi_scan_root, among other things uses device_is_managed_by_native_pciehp()
> > > to determine if a given slot has pcie hotplug capabilties, whcih checks the
> > > devices OSC_PCI_EXPRESS_NATIVE_HP_CONTROL flag. Since that flag is not set
> > > until after pci_acpi_scan_root_completes, the acpi code never sees that pcie
> > > slots are hotplug capable and configures them all to use acpi instead.
> > >
> > > Fix is pretty simple, just defer the scan until after the osc flags have been
> > > set on the device. Tested by myself and it seems to work well.
> > >
> > > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > > CC: Len Brown <lenb@...nel.org>
> > > CC: "Rafael J. Wysocki" <rjw@...k.pl>
> > > CC: linux-acpi@...r.kernel.org
> > > ---
> > > drivers/acpi/pci_root.c | 41 ++++++++++++++++++++---------------------
> > > 1 file changed, 20 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > > index 5917839..a2c2661 100644
> > > --- a/drivers/acpi/pci_root.c
> > > +++ b/drivers/acpi/pci_root.c
> > > @@ -437,27 +437,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
> > > flags = base_flags = OSC_PCI_SEGMENT_GROUPS_SUPPORT;
> > > acpi_pci_osc_support(root, flags);
> > >
> > > - /*
> > > - * TBD: Need PCI interface for enumeration/configuration of roots.
> > > - */
> > > -
> > > - /*
> > > - * Scan the Root Bridge
> > > - * --------------------
> > > - * Must do this prior to any attempt to bind the root device, as the
> > > - * PCI namespace does not get created until this call is made (and
> > > - * thus the root bridge's pci_dev does not exist).
> > > - */
> > > - root->bus = pci_acpi_scan_root(root);
> > > - if (!root->bus) {
> > > - dev_err(&device->dev,
> > > - "Bus %04x:%02x not present in PCI namespace\n",
> > > - root->segment, (unsigned int)root->secondary.start);
> > > - result = -ENODEV;
> > > - goto end;
> > > - }
> > > -
> > > - /* Indicate support for various _OSC capabilities. */
> > > if (pci_ext_cfg_avail())
> > > flags |= OSC_EXT_PCI_CONFIG_SUPPORT;
> > > if (pcie_aspm_support_enabled()) {
> > > @@ -520,6 +499,26 @@ static int acpi_pci_root_add(struct acpi_device *device,
> > > "(_OSC support mask: 0x%02x)\n", flags);
> > > }
> > >
> > > + /*
> > > + * TBD: Need PCI interface for enumeration/configuration of roots.
> > > + */
> > > +
> > > + /*
> > > + * Scan the Root Bridge
> > > + * --------------------
> > > + * Must do this prior to any attempt to bind the root device, as the
> > > + * PCI namespace does not get created until this call is made (and
> > > + * thus the root bridge's pci_dev does not exist).
> > > + */
> > > + root->bus = pci_acpi_scan_root(root);
> > > + if (!root->bus) {
> > > + dev_err(&device->dev,
> > > + "Bus %04x:%02x not present in PCI namespace\n",
> > > + root->segment, (unsigned int)root->secondary.start);
> > > + result = -ENODEV;
> > > + goto end;
> > > + }
> > > +
> > > pci_acpi_add_bus_pm_notifier(device, root->bus);
> > > if (device->wakeup.flags.run_wake)
> > > device_set_run_wake(root->bus->bridge, true);
> > >
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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