powerpc/pseries: Round up MSI-X requests

The pseries firmware currently refuses any non power of two MSI-X
request. Unfortunately most network drivers end up asking for that
because they want a power of two for RX queues and one or two extra
for everything else.

This patch rounds up the firmware request to the next power of two
if the quota allows it. If this fails we fall back to using the
original request size.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/msi.c

@@ -387,12 +387,13 @@ static int check_msix_entries(struct pci_dev *pdev)
 	return 0;
 }
 
-static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
+static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec_in, int type)
 {
 	struct pci_dn *pdn;
 	int hwirq, virq, i, rc;
 	struct msi_desc *entry;
 	struct msi_msg msg;
+	int nvec = nvec_in;
 
 	pdn = get_pdn(pdev);
 	if (!pdn)
@@ -401,11 +402,24 @@ static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
 	if (type == PCI_CAP_ID_MSIX && check_msix_entries(pdev))
 		return -EINVAL;
 
+	/*
+	 * Firmware currently refuse any non power of two allocation
+	 * so we round up if the quota will allow it.
+	 */
+	if (type == PCI_CAP_ID_MSIX) {
+		int m = roundup_pow_of_two(nvec);
+		int quota = msi_quota_for_device(pdev, m);
+
+		if (quota >= m)
+			nvec = m;
+	}
+
 	/*
 	 * Try the new more explicit firmware interface, if that fails fall
 	 * back to the old interface. The old interface is known to never
 	 * return MSI-Xs.
 	 */
+again:
 	if (type == PCI_CAP_ID_MSI) {
 		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSI_FN, nvec);
 
@@ -417,6 +431,10 @@ static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
 		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSIX_FN, nvec);
 
 	if (rc != nvec) {
+		if (nvec != nvec_in) {
+			nvec = nvec_in;
+			goto again;
+		}
 		pr_debug("rtas_msi: rtas_change_msi() failed\n");
 		return rc;
 	}