PCI: don't enable too many HT MSI mappings

Prakash reported that his c51-mcp51 ondie sound card doesn't work with
MSI.  But if he hacks out the HT-MSI quirk, MSI works fine.

So this patch reworks the nv_msi_ht_cap_quirk().  It will now only
enable ht_msi on own its root device, avoiding enabling it on devices
following that root dev.

Reported-by: Prakash Punnoor <prakash@punnoor.de>
Tested-by: Prakash Punnoor <prakash@punnoor.de>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@hobbes.lan>

drivers/pci/quirks.c

@@ -2050,10 +2050,100 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA,
 			PCI_DEVICE_ID_NVIDIA_NVENET_15,
 			nvenet_msi_disable);
 
+static void __devinit nv_ht_enable_msi_mapping(struct pci_dev *dev)
+{
+	struct pci_dev *host_bridge;
+	int pos;
+	int i, dev_no;
+	int found = 0;
+
+	dev_no = dev->devfn >> 3;
+	for (i = dev_no; i >= 0; i--) {
+		host_bridge = pci_get_slot(dev->bus, PCI_DEVFN(i, 0));
+		if (!host_bridge)
+			continue;
+
+		pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE);
+		if (pos != 0) {
+			found = 1;
+			break;
+		}
+		pci_dev_put(host_bridge);
+	}
+
+	if (!found)
+		return;
+
+	/* root did that ! */
+	if (msi_ht_cap_enabled(host_bridge))
+		goto out;
+
+	ht_enable_msi_mapping(dev);
+
+out:
+	pci_dev_put(host_bridge);
+}
+
+static void __devinit ht_disable_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
+					 &flags) == 0) {
+			dev_info(&dev->dev, "Enabling HT MSI Mapping\n");
+
+			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
+					      flags & ~HT_MSI_FLAGS_ENABLE);
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+						  HT_CAPTYPE_MSI_MAPPING);
+	}
+}
+
+static int __devinit ht_check_msi_mapping(struct pci_dev *dev)
+{
+	int pos, ttl = 48;
+	int found = 0;
+
+	/* check if there is HT MSI cap or enabled on this device */
+	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
+	while (pos && ttl--) {
+		u8 flags;
+
+		if (found < 1)
+			found = 1;
+		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
+					 &flags) == 0) {
+			if (flags & HT_MSI_FLAGS_ENABLE) {
+				if (found < 2) {
+					found = 2;
+					break;
+				}
+			}
+		}
+		pos = pci_find_next_ht_capability(dev, pos,
+						  HT_CAPTYPE_MSI_MAPPING);
+	}
+
+	return found;
+}
+
 static void __devinit nv_msi_ht_cap_quirk(struct pci_dev *dev)
 {
 	struct pci_dev *host_bridge;
-	int pos, ttl = 48;
+	int pos;
+	int found;
+
+	/* check if there is HT MSI cap or enabled on this device */
+	found = ht_check_msi_mapping(dev);
+
+	/* no HT MSI CAP */
+	if (found == 0)
+		return;
 
 	/*
 	 * HT MSI mapping should be disabled on devices that are below
@@ -2069,24 +2159,19 @@ static void __devinit nv_msi_ht_cap_quirk(struct pci_dev *dev)
 	pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE);
 	if (pos != 0) {
 		/* Host bridge is to HT */
-		ht_enable_msi_mapping(dev);
+		if (found == 1) {
+			/* it is not enabled, try to enable it */
+			nv_ht_enable_msi_mapping(dev);
+		}
 		return;
 	}
 
-	/* Host bridge is not to HT, disable HT MSI mapping on this device */
-	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
-	while (pos && ttl--) {
-		u8 flags;
+	/* HT MSI is not enabled */
+	if (found == 1)
+		return;
 
-		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
-					 &flags) == 0) {
-			dev_info(&dev->dev, "Disabling HT MSI mapping");
-			pci_write_config_byte(dev, pos + HT_MSI_FLAGS,
-					      flags & ~HT_MSI_FLAGS_ENABLE);
-		}
-		pos = pci_find_next_ht_capability(dev, pos,
-						  HT_CAPTYPE_MSI_MAPPING);
-	}
+	/* Host bridge is not to HT, disable HT MSI mapping on this device */
+	ht_disable_msi_mapping(dev);
 }
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID, nv_msi_ht_cap_quirk);
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AL, PCI_ANY_ID, nv_msi_ht_cap_quirk);