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Date: Fri, 23 Aug 2013 14:46:23 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: "Rafael J. Wysocki" <rjw@...k.pl>
Cc: Neil Horman <nhorman@...driver.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Len Brown <lenb@...nel.org>,
"linux-acpi@...r.kernel.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 Fri, Aug 23, 2013 at 2:53 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> 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?
My opinion is that the _OSC/ASPM state management is ridiculously
complicated already, and this would make it slightly more complicated.
That's why my preference would be to attempt a more radical cleanup
and simplification instead of adding another wart.
But if you want to merge a patch along the lines of what Neil
proposes, I won't object.
Bjorn
>> > 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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