mei: add mei_quirk_probe function

commit 9a123f19 upstream.

The main purpose of this function is to exclude ME devices
without support for MEI/HECI interface from binding

Currently affected systems are C600/X79 based servers
that expose PCI device even though it doesn't supported ME Interface.
MEI driver accessing such nonfunctional device can corrupt
the system.

[Backported to 3.2: files were moved]
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/staging/mei/main.c

@@ -105,6 +105,27 @@ MODULE_DEVICE_TABLE(pci, mei_pci_tbl);
 
 static DEFINE_MUTEX(mei_mutex);
 
+/**
+ * mei_quirk_probe - probe for devices that doesn't valid ME interface
+ * @pdev: PCI device structure
+ * @ent: entry into pci_device_table
+ *
+ * returns true if ME Interface is valid, false otherwise
+ */
+static bool __devinit mei_quirk_probe(struct pci_dev *pdev,
+				const struct pci_device_id *ent)
+{
+	u32 reg;
+	if (ent->device == MEI_DEV_ID_PBG_1) {
+		pci_read_config_dword(pdev, 0x48, &reg);
+		/* make sure that bit 9 is up and bit 10 is down */
+		if ((reg & 0x600) == 0x200) {
+			dev_info(&pdev->dev, "Device doesn't have valid ME Interface\n");
+			return false;
+		}
+	}
+	return true;
+}
 /**
  * mei_probe - Device Initialization Routine
  *
@@ -120,6 +141,12 @@ static int __devinit mei_probe(struct pci_dev *pdev,
 	int err;
 
 	mutex_lock(&mei_mutex);
+
+	if (!mei_quirk_probe(pdev, ent)) {
+		err = -ENODEV;
+		goto end;
+	}
+
 	if (mei_device) {
 		err = -EEXIST;
 		goto end;