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authorBjorn Helgaas <bhelgaas@google.com>2013-05-21 10:56:51 -0600
committerBjorn Helgaas <bhelgaas@google.com>2013-05-21 10:56:51 -0600
commit2add0ec14c259471d45d6afd051ca02eef0a4a92 (patch)
treef863949b30c8a3e0b3096b1284096a6e675069b7
parentde7f2b1bdf02f6b44410dceb7295284c2a75a304 (diff)
downloadop-kernel-dev-2add0ec14c259471d45d6afd051ca02eef0a4a92.zip
op-kernel-dev-2add0ec14c259471d45d6afd051ca02eef0a4a92.tar.gz
PCI/ASPM: Warn when driver asks to disable ASPM, but we can't do it
Some devices have hardware problems related to using ASPM. Drivers for these devices use pci_disable_link_state() to prevent their device from entering L0s or L1. But on platforms where the OS doesn't have permission to manage ASPM, pci_disable_link_state() doesn't actually disable ASPM. Windows has a similar mechanism ("PciASPMOptOut"), and when the OS doesn't have control of ASPM, it doesn't actually disable ASPM either. This patch just adds a warning in dmesg about the fact that pci_disable_link_state() is doing nothing. Reported-by: Emmanuel Grumbach <egrumbach@gmail.com> Reference: https://lkml.kernel.org/r/CANUX_P3F5YhbZX3WGU-j1AGpbXb_T9Bis2ErhvKkFMtDvzatVQ@mail.gmail.com Reference: https://bugzilla.kernel.org/show_bug.cgi?id=57331 Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
-rw-r--r--drivers/pci/pcie/aspm.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index d320df6..faa83b6 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -724,9 +724,6 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem,
struct pci_dev *parent = pdev->bus->self;
struct pcie_link_state *link;
- if (aspm_disabled && !force)
- return;
-
if (!pci_is_pcie(pdev))
return;
@@ -736,6 +733,19 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem,
if (!parent || !parent->link_state)
return;
+ /*
+ * A driver requested that ASPM be disabled on this device, but
+ * if we don't have permission to manage ASPM (e.g., on ACPI
+ * systems we have to observe the FADT ACPI_FADT_NO_ASPM bit and
+ * the _OSC method), we can't honor that request. Windows has
+ * a similar mechanism using "PciASPMOptOut", which is also
+ * ignored in this situation.
+ */
+ if (aspm_disabled && !force) {
+ dev_warn(&pdev->dev, "can't disable ASPM; OS doesn't have ASPM control\n");
+ return;
+ }
+
if (sem)
down_read(&pci_bus_sem);
mutex_lock(&aspm_lock);
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