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+

1 files changed, 37 insertions, 39 deletions

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 0ac546d5e53f..c740364d4abe 100644
--- 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);