PCI/ASPM: Warn when driver asks to disable ASPM, but we can't do it (2add0ec1) · Commits · 戴 / test

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>

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);

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