PCI: Refactor HT advertising of NO_MSI flag

The few quirks that deal with NO_MSI tend to be copy-paste heavy.
Refactor them so that the hierarchy of conditions is slightly
cleaner.

Link: https://lore.kernel.org/r/20210330151145.997953-15-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Author: Marc Zyngier

drivers/pci/quirks.c

@@ -2585,10 +2585,8 @@ static int msi_ht_cap_enabled(struct pci_dev *dev)
 /* Check the HyperTransport MSI mapping to know whether MSI is enabled or not */
 static void quirk_msi_ht_cap(struct pci_dev *dev)
 {
-	if (dev->subordinate && !msi_ht_cap_enabled(dev)) {
-		pci_warn(dev, "MSI quirk detected; subordinate MSI disabled\n");
-		dev->subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
-	}
+	if (!msi_ht_cap_enabled(dev))
+		quirk_disable_msi(dev);
 }
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_HT2000_PCIE,
 			quirk_msi_ht_cap);
@@ -2601,20 +2599,15 @@ static void quirk_nvidia_ck804_msi_ht_cap(struct pci_dev *dev)
 {
 	struct pci_dev *pdev;
 
-	if (!dev->subordinate)
-		return;
-
 	/*
 	 * Check HT MSI cap on this chipset and the root one.  A single one
 	 * having MSI is enough to be sure that MSI is supported.
 	 */
 	pdev = pci_get_slot(dev->bus, 0);
 	if (!pdev)
 		return;
-	if (!msi_ht_cap_enabled(dev) && !msi_ht_cap_enabled(pdev)) {
-		pci_warn(dev, "MSI quirk detected; subordinate MSI disabled\n");
-		dev->subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
-	}
+	if (!msi_ht_cap_enabled(pdev))
+		quirk_msi_ht_cap(dev);
 	pci_dev_put(pdev);
 }
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,