PCI/MSI: Free legacy IRQ when enabling MSI/MSI-X

Once MSI/MSI-X is enabled by the device driver, a PCI device won't use
legacy IRQs again until MSI/MSI-X is disabled.

Call pcibios_free_irq() when enabling MSI/MSI-X and pcibios_alloc_irq()
when disabling MSI/MSI-X.  This allows arch code to manage resources
associated with the legacy IRQ.

[bhelgaas: changelog]
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

drivers/pci/msi.c

@@ -665,6 +665,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec)
 	pci_msi_set_enable(dev, 1);
 	dev->msi_enabled = 1;
 
+	pcibios_free_irq(dev);
 	dev->irq = entry->irq;
 	return 0;
 }
@@ -792,9 +793,9 @@ static int msix_capability_init(struct pci_dev *dev,
 	/* Set MSI-X enabled bits and unmask the function */
 	pci_intx_for_msi(dev, 0);
 	dev->msix_enabled = 1;
-
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
 
+	pcibios_free_irq(dev);
 	return 0;
 
 out_avail:
@@ -909,6 +910,7 @@ void pci_msi_shutdown(struct pci_dev *dev)
 
 	/* Restore dev->irq to its default pin-assertion irq */
 	dev->irq = desc->msi_attrib.default_irq;
+	pcibios_alloc_irq(dev);
 }
 
 void pci_disable_msi(struct pci_dev *dev)
@@ -1009,6 +1011,7 @@ void pci_msix_shutdown(struct pci_dev *dev)
 	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
 	pci_intx_for_msi(dev, 1);
 	dev->msix_enabled = 0;
+	pcibios_alloc_irq(dev);
 }
 
 void pci_disable_msix(struct pci_dev *dev)