On Mon, Aug 26, 2013 at 11:39:13AM -0400, 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@xxxxxxxxxxxxx>
> CC: Len Brown <lenb@xxxxxxxxxx>
> CC: "Rafael J. Wysocki" <rjw@xxxxxxx>
> CC: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> CC: linux-acpi@xxxxxxxxxxxxxxx
> CC: linux-pci@xxxxxxxxxxxxxxx
>
> ---
> Change notes:
> v2) eferred the disabling of aspm until after the acpi scan of the pci bus is
> complete. This was done to allow proper handling of pcie 1.1 devices, as per:
>
> commit b8178f130e25c1bdac1c33e0996f1ff6e20ec08e
> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Date: Mon Apr 1 15:47:39 2013 -0600
>
> Revert "PCI/ACPI: Request _OSC control before scanning PCI root bus"
>
> As discussed previously in the thread the disable logic for aspm needs to be
> untangled and refactored, which is not something I'm sufficently versed in teh
> hotplug code to do right now, but this fixes the problem above, and prevents the
> problem that necessitated the revert without adding any visible complexity to
> the user, so I think its ok.
>
> v3) Fixup stupid authorship error
> ---
> drivers/acpi/pci_root.c | 54 +++++++++++++++++++++++++++++--------------------
> 1 file changed, 32 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 5917839..1e80a90 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -378,6 +378,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
> struct acpi_pci_root *root;
> u32 flags, base_flags;
> acpi_handle handle = device->handle;
> + bool no_aspm = false;
>
> root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
> if (!root)
> @@ -437,27 +438,6 @@ 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()) {
> @@ -512,7 +492,14 @@ static int acpi_pci_root_add(struct acpi_device *device,
> acpi_format_exception(status), flags);
> dev_info(&device->dev,
> "ACPI _OSC control for PCIe not granted, disabling ASPM\n");
> - pcie_no_aspm();
> + /*
> + * We want to disable aspm here, but aspm_disabled
> + * needs to remain in its state from boot so that we
> + * properly handle pcie 1.1 devices. So we set this
> + * flag here, to defer the action until after the acpi
> + * root scan
> + */
> + no_aspm = true;
> }
> } else {
> dev_info(&device->dev,
> @@ -520,6 +507,29 @@ 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;
> + }
> +
> + if (no_aspm)
> + pcie_no_aspm();
> +
> pci_acpi_add_bus_pm_notifier(device, root->bus);
> if (device->wakeup.flags.run_wake)
> device_set_run_wake(root->bus->bridge, true);
I think there are two problems with this patch:
1) There's another call of pcie_no_aspm() at line 454 (in the
error path when acpi_pci_osc_support() fails), which happens
before scanning the bus. I think this needs to be converted to
"no_aspm = true" as you did for the one in the error path when
acpi_pci_osc_control_set() fails.
2) You effectively moved the call of "pcie_clear_aspm(root->bus)"
so it now happens before scanning the bus, which will cause a
NULL pointer dereference if we take that path.
I think we need something like the patch below on top of your
v3 patch. Can you take a look and see if this makes sense, and
if so, update your patch to include these or similar fixes?
Here are my notes about where the ASPM and root->osc_control_set
setting and testing happen.
Before your patch:
acpi_pci_root_add
root = kzalloc # root->osc_control_set = 0
acpi_pci_osc_support # indicate OS support for segments
root->bus = pci_acpi_scan_root # SCAN BUS
pci_create_root_bus
pcibios_add_bus
acpi_pci_add_bus
acpiphp_enumerate_slots
acpi_walk_namespace(..., register_slot, ...)
register_slot
device_is_managed_by_native_pciehp
<test root->osc_control_set> # root->osc_control_set == 0
return if OS has PCIe hotplug control (we never do)
acpiphp_register_hotplug_slot (so we always do this)
acpi_pci_osc_support # indicate OS support for MSI, ASPM, etc
if (_osc_support() failed)
pci_no_aspm
acpi_pci_osc_control_set # request OS control of hotplug, PME, AER, etc
root->osc_control_set = XX
if (_osc_control_set() succeeded) {
if (FADT NO_ASPM bit)
pcie_clear_aspm
list_for_each_entry(..., &bus->devices, ...)
} else
pcie_no_aspm # _osc_control_set() failed
After your patch:
acpi_pci_root_add
root = kzalloc # root->osc_control_set = 0
acpi_pci_osc_support # indicate OS support for segments
if (_osc_support() failed)
pci_no_aspm # ** (1) before bus scan
acpi_pci_osc_support # indicate OS support for MSI, ASPM, etc
acpi_pci_osc_control_set # request OS control of hotplug, PME, AER, etc
root->osc_control_set = XX
if (_osc_control_set() succeeded) {
if (FADT NO_ASPM bit)
pcie_clear_aspm(root->bus) # ** (2) root->bus == NULL
list_for_each_entry(..., &bus->devices, ...)
} else
no_aspm = true # _osc_control_set() failed
root->bus = pci_acpi_scan_root # SCAN BUS
pci_create_root_bus
pcibios_add_bus
acpi_pci_add_bus
acpiphp_enumerate_slots
acpi_walk_namespace(..., register_slot, ...)
register_slot
device_is_managed_by_native_pciehp
<test root->osc_control_set>
return if OS has PCIe hotplug control
acpiphp_register_hotplug_slot
if (no_aspm)
pcie_no_aspm
Bjorn
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index a37a372..a67853e 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -378,7 +378,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
struct acpi_pci_root *root;
u32 flags, base_flags;
acpi_handle handle = device->handle;
- bool no_aspm = false;
+ bool no_aspm = false, clear_aspm = false;
root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
if (!root)
@@ -451,7 +451,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
if (ACPI_FAILURE(status)) {
dev_info(&device->dev, "ACPI _OSC support "
"notification failed, disabling PCIe ASPM\n");
- pcie_no_aspm();
+ no_aspm = true;
flags = base_flags;
}
}
@@ -483,7 +483,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
* We have ASPM control, but the FADT indicates
* that it's unsupported. Clear it.
*/
- pcie_clear_aspm(root->bus);
+ clear_aspm = true;
}
} else {
dev_info(&device->dev,
@@ -527,6 +527,10 @@ static int acpi_pci_root_add(struct acpi_device *device,
goto end;
}
+ if (clear_aspm) {
+ dev_info(&device->dev, "Disabling ASPM (FADT indicates it is unsupported)\n");
+ pcie_clear_aspm(root->bus);
+ }
if (no_aspm)
pcie_no_aspm();
--
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