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Commit 2add0ec1 authored by Bjorn Helgaas's avatar Bjorn Helgaas
Browse files

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: default avatarEmmanuel 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: default avatarBjorn Helgaas <bhelgaas@google.com>
parent de7f2b1b

drivers/pci/pcie/aspm.c

+13 −3
Original line number Diff line number Diff line
@@ -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);