PCI: Add pcibios_sriov_enable() and pcibios_sriov_disable()

VFs are dynamically created when a driver enables them.  On some platforms,
like PowerNV, special resources are necessary to enable VFs.

Add platform hooks for enabling and disabling VFs.

Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

drivers/pci/iov.c

@@ -220,6 +220,11 @@ static void virtfn_remove(struct pci_dev *dev, int id, int reset)
 	pci_dev_put(dev);
 }
 
+int __weak pcibios_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
+{
+       return 0;
+}
+
 static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
 {
 	int rc;
@@ -231,6 +236,7 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
 	struct pci_sriov *iov = dev->sriov;
 	int bars = 0;
 	int bus;
+	int retval;
 
 	if (!nr_virtfn)
 		return 0;
@@ -307,6 +313,12 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
 	if (nr_virtfn < initial)
 		initial = nr_virtfn;
 
+	if ((retval = pcibios_sriov_enable(dev, initial))) {
+		dev_err(&dev->dev, "failure %d from pcibios_sriov_enable()\n",
+			retval);
+		return retval;
+	}
+
 	for (i = 0; i < initial; i++) {
 		rc = virtfn_add(dev, i, 0);
 		if (rc)
@@ -335,6 +347,11 @@ failed:
 	return rc;
 }
 
+int __weak pcibios_sriov_disable(struct pci_dev *pdev)
+{
+       return 0;
+}
+
 static void sriov_disable(struct pci_dev *dev)
 {
 	int i;
@@ -346,6 +363,8 @@ static void sriov_disable(struct pci_dev *dev)
 	for (i = 0; i < iov->num_VFs; i++)
 		virtfn_remove(dev, i, 0);
 
+	pcibios_sriov_disable(dev);
+
 	iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
 	pci_cfg_access_lock(dev);
 	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);