54 lines
2.0 KiB
Diff
54 lines
2.0 KiB
Diff
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From: Matthew Garrett <mjg@redhat.com>
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Subject: ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe
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ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe
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The PCI SIG documentation for the _OSC OS/firmware handshaking interface
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states:
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"If the _OSC control method is absent from the scope of a host bridge
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device, then the operating system must not enable or attempt to use any
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features defined in this section for the hierarchy originated by the host
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bridge."
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The obvious interpretation of this is that the OS should not attempt to use
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PCIe hotplug, PME or AER - however, the specification also notes that an
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_OSC method is *required* for PCIe hierarchies, and experimental validation
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with An Alternative OS indicates that it doesn't use any PCIe functionality
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if the _OSC method is missing. That arguably means we shouldn't be using
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MSI or extended config space, but right now our problems seem to be limited
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to vendors being surprised when ASPM gets enabled on machines when other
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OSs refuse to do so. So, for now, let's just disable ASPM if the _OSC
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method doesn't exist or refuses to hand over PCIe capability control.
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Signed-off-by: Matthew Garrett <mjg@redhat.com>
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---
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diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
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index 4eac593..1f67057 100644
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--- a/drivers/acpi/pci_root.c
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+++ b/drivers/acpi/pci_root.c
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@@ -33,6 +33,7 @@
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#include <linux/pm_runtime.h>
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#include <linux/pci.h>
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#include <linux/pci-acpi.h>
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+#include <linux/pci-aspm.h>
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#include <linux/acpi.h>
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#include <linux/slab.h>
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#include <acpi/acpi_bus.h>
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@@ -543,6 +544,14 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device)
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if (flags != base_flags)
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acpi_pci_osc_support(root, flags);
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+ status = acpi_pci_osc_control_set(root->device->handle,
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+ 0);
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+
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+ if (status == AE_NOT_EXIST) {
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+ printk(KERN_INFO "Unable to assume PCIe control: Disabling ASPM\n");
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+ pcie_no_aspm();
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+ }
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+
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pci_acpi_add_bus_pm_notifier(device, root->bus);
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if (device->wakeup.flags.run_wake)
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device_set_run_wake(root->bus->bridge, true);
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