Revert "PCI/ACPI: Request _OSC control before scanning PCI root bus"

This reverts commit 8c33f51df406e1a1f7fa4e9b244845b7ebd61fa6.

Conflicts:
	drivers/acpi/pci_root.c

This commit broke some pre-1.1 PCIe devices by leaving them with
ASPM enabled.  Previously, we had disabled ASPM on these devices
because many of them don't implement it correctly (per 149e1637).

Requesting _OSC control early means that aspm_disabled may be set
before we scan the PCI bus and configure link ASPM state.  But the
ASPM configuration currently skips the check for pre-PCIe 1.1 devices
when aspm_disabled is set, like this:

    acpi_pci_root_add
      acpi_pci_osc_support
        if (flags != base_flags)
          pcie_no_aspm
            aspm_disabled = 1
      pci_acpi_scan_root
        ...
          pcie_aspm_init_link_state
            pcie_aspm_sanity_check
              if (!aspm_disabled)
                /* check for pre-PCIe 1.1 device */

Therefore, setting aspm_disabled early means that we leave ASPM enabled
on these pre-PCIe 1.1 devices, which is a regression for some devices.

The best fix would be to clean up the ASPM init so we can evaluate
_OSC before scanning the bug (that way boot-time and hot-add discovery
will work the same), but that requires significant rework.

For now, we'll just revert the _OSC change as the lowest-risk fix.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=55211
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
CC: stable@vger.kernel.org	# v3.8+

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 0ac546d..c740364 100644 (file)
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -415,7 +415,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
        struct acpi_pci_root *root;
        struct acpi_pci_driver *driver;
        u32 flags, base_flags;
-       bool is_osc_granted = false;
 
        root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
        if (!root)
@@ -476,6 +475,30 @@ 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.
+        */
+
+       mutex_lock(&acpi_pci_root_lock);
+       list_add_tail(&root->node, &acpi_pci_roots);
+       mutex_unlock(&acpi_pci_root_lock);
+
+       /*
+        * 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) {
+               printk(KERN_ERR PREFIX
+                           "Bus %04x:%02x not present in PCI namespace\n",
+                           root->segment, (unsigned int)root->secondary.start);
+               result = -ENODEV;
+               goto out_del_root;
+       }
+
        /* Indicate support for various _OSC capabilities. */
        if (pci_ext_cfg_avail())
                flags |= OSC_EXT_PCI_CONFIG_SUPPORT;
@@ -494,6 +517,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
                        flags = base_flags;
                }
        }
+
        if (!pcie_ports_disabled
            && (flags & ACPI_PCIE_REQ_SUPPORT) == ACPI_PCIE_REQ_SUPPORT) {
                flags = OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL
@@ -514,54 +538,28 @@ static int acpi_pci_root_add(struct acpi_device *device,
                status = acpi_pci_osc_control_set(device->handle, &flags,
                                       OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL);
                if (ACPI_SUCCESS(status)) {
-                       is_osc_granted = true;
                        dev_info(&device->dev,
                                "ACPI _OSC control (0x%02x) granted\n", flags);
+                       if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
+                               /*
+                                * We have ASPM control, but the FADT indicates
+                                * that it's unsupported. Clear it.
+                                */
+                               pcie_clear_aspm(root->bus);
+                       }
                } else {
-                       is_osc_granted = false;
                        dev_info(&device->dev,
                                "ACPI _OSC request failed (%s), "
                                "returned control mask: 0x%02x\n",
                                acpi_format_exception(status), flags);
+                       pr_info("ACPI _OSC control for PCIe not granted, "
+                               "disabling ASPM\n");
+                       pcie_no_aspm();
                }
        } else {
                dev_info(&device->dev,
-                       "Unable to request _OSC control "
-                       "(_OSC support mask: 0x%02x)\n", flags);
-       }
-
-       /*
-        * TBD: Need PCI interface for enumeration/configuration of roots.
-        */
-
-       mutex_lock(&acpi_pci_root_lock);
-       list_add_tail(&root->node, &acpi_pci_roots);
-       mutex_unlock(&acpi_pci_root_lock);
-
-       /*
-        * 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) {
-               printk(KERN_ERR PREFIX
-                           "Bus %04x:%02x not present in PCI namespace\n",
-                           root->segment, (unsigned int)root->secondary.start);
-               result = -ENODEV;
-               goto out_del_root;
-       }
-
-       /* ASPM setting */
-       if (is_osc_granted) {
-               if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM)
-                       pcie_clear_aspm(root->bus);
-       } else {
-               pr_info("ACPI _OSC control for PCIe not granted, "
-                       "disabling ASPM\n");
-               pcie_no_aspm();
+                        "Unable to request _OSC control "
+                        "(_OSC support mask: 0x%02x)\n", flags);
        }
 
        pci_acpi_add_bus_pm_notifier(device, root->bus);