PCI: Don't clear ASPM bits when the FADT declares it's unsupported

Communications with a hardware vendor confirm that the expected behaviour
on systems that set the FADT ASPM disable bit but which still grant full
PCIe control is for the OS to leave any BIOS configuration intact and
refuse to touch the ASPM bits.  This mimics the behaviour of Windows.

Signed-off-by: Matthew Garrett <mjg59@coreos.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 68a5f712cd198e5cd61b866d2068b9d52a1274f4..1b5569c092c6e205a784257f88d6f1ad06c5c3be 100644 (file)
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -423,8 +423,7 @@ out:
 }
 EXPORT_SYMBOL(acpi_pci_osc_control_set);
 
-static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
-                                int *clear_aspm)
+static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 {
        u32 support, control, requested;
        acpi_status status;
@@ -495,10 +494,12 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
                decode_osc_control(root, "OS now controls", control);
                if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
                        /*
-                        * We have ASPM control, but the FADT indicates
-                        * that it's unsupported. Clear it.
+                        * We have ASPM control, but the FADT indicates that
+                        * it's unsupported. Leave existing configuration
+                        * intact and prevent the OS from touching it.
                         */
-                       *clear_aspm = 1;
+                       dev_info(&device->dev, "FADT indicates ASPM is unsupported, using BIOS configuration\n");
+                       *no_aspm = 1;
                }
        } else {
                decode_osc_control(root, "OS requested", requested);
@@ -525,7 +526,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
        int result;
        struct acpi_pci_root *root;
        acpi_handle handle = device->handle;
-       int no_aspm = 0, clear_aspm = 0;
+       int no_aspm = 0;
        bool hotadd = system_state != SYSTEM_BOOTING;
 
        root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
@@ -584,7 +585,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
 
        root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
 
-       negotiate_os_control(root, &no_aspm, &clear_aspm);
+       negotiate_os_control(root, &no_aspm);
 
        /*
         * TBD: Need PCI interface for enumeration/configuration of roots.
@@ -607,10 +608,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
                goto remove_dmar;
        }
 
-       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();
 

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 820740a22e94535a95bc4ed4e242435d6225709e..7d4fcdc512aa0ab5d4768b94272eb8359a2599cb 100644 (file)
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -782,24 +782,6 @@ void pci_disable_link_state(struct pci_dev *pdev, int state)
 }
 EXPORT_SYMBOL(pci_disable_link_state);
 
-void pcie_clear_aspm(struct pci_bus *bus)
-{
-       struct pci_dev *child;
-
-       if (aspm_force)
-               return;
-
-       /*
-        * Clear any ASPM setup that the firmware has carried out on this bus
-        */
-       list_for_each_entry(child, &bus->devices, bus_list) {
-               __pci_disable_link_state(child, PCIE_LINK_STATE_L0S |
-                                        PCIE_LINK_STATE_L1 |
-                                        PCIE_LINK_STATE_CLKPM,
-                                        false, true);
-       }
-}
-
 static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp)
 {
        int i;

diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
index 8af4610c2e414963a62e4522b482afa700ec4532..207c561fb40ef000feeda342d1f681349df4b99b 100644 (file)
--- a/include/linux/pci-aspm.h
+++ b/include/linux/pci-aspm.h
@@ -29,7 +29,6 @@ void pcie_aspm_pm_state_change(struct pci_dev *pdev);
 void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
 void pci_disable_link_state(struct pci_dev *pdev, int state);
 void pci_disable_link_state_locked(struct pci_dev *pdev, int state);
-void pcie_clear_aspm(struct pci_bus *bus);
 void pcie_no_aspm(void);
 #else
 static inline void pcie_aspm_init_link_state(struct pci_dev *pdev)
@@ -47,9 +46,6 @@ static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
 static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
 {
 }
-static inline void pcie_clear_aspm(struct pci_bus *bus)
-{
-}
 static inline void pcie_no_aspm(void)
 {
 }