PCI: shpchp: Enable bridge bus mastering if MSI is enabled

commit 48b79a1 upstream.

An SHPC may generate MSIs to notify software about slot or controller
events (SHPC spec r1.0, sec 4.7).  A PCI device can only generate an MSI if
it has bus mastering enabled.

Enable bus mastering if the bridge contains an SHPC that uses MSI for event
notifications.

Signed-off-by: Aleksandr Bezzubikov <zuban32s@gmail.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/pci/hotplug/shpchp_hpc.c

@@ -1062,6 +1062,8 @@ int shpc_init(struct controller *ctrl, struct pci_dev *pdev)
 		if (rc) {
 			ctrl_info(ctrl, "Can't get msi for the hotplug controller\n");
 			ctrl_info(ctrl, "Use INTx for the hotplug controller\n");
+		} else {
+			pci_set_master(pdev);
 		}
 
 		rc = request_irq(ctrl->pci_dev->irq, shpc_isr, IRQF_SHARED,