PCI: vmd: Fix potential deadlock when enabling ASPM

commit 49de0dc upstream.

The vmd_pm_enable_quirk() helper is called from pci_walk_bus() during
probe to enable ASPM for controllers with VMD_FEAT_BIOS_PM_QUIRK set.

Since pci_walk_bus() already holds a pci_bus_sem read lock, use
pci_enable_link_state_locked() to enable link states in order to avoid a
potential deadlock (e.g. in case someone takes a write lock before
reacquiring the read lock).

Fixes: f492edb ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
Link: https://lore.kernel.org/r/20231128081512.19387-3-johan+linaro@kernel.org
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
[bhelgaas: add "potential" in subject since the deadlock has only been
reported by lockdep, include helper name in commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: <stable@vger.kernel.org>	# 6.3
Cc: Michael Bottini <michael.a.bottini@linux.intel.com>
Cc: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/pci/controller/vmd.c

@@ -751,7 +751,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 	if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
 		return 0;
 
-	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
+	pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
 
 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
 	if (!pos)