PCI: Wait for pending transactions to complete before 82599 FLR

Before initiating an FLR, we should wait for completion of any outstanding
non-posted requests.  See PCIe spec r3.0, sec 6.6.2.

This makes reset_intel_82599_sfp_virtfn() very similar to the generic
pcie_flr().  The only difference is that the 82599 doesn't report FLR
support in the VF Device Capability register.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/quirks.c

@@ -3081,10 +3081,36 @@ static int reset_intel_generic_dev(struct pci_dev *dev, int probe)
 
 static int reset_intel_82599_sfp_virtfn(struct pci_dev *dev, int probe)
 {
+	int i;
+	u16 status;
+
+	/*
+	 * http://www.intel.com/content/dam/doc/datasheet/82599-10-gbe-controller-datasheet.pdf
+	 *
+	 * The 82599 supports FLR on VFs, but FLR support is reported only
+	 * in the PF DEVCAP (sec 9.3.10.4), not in the VF DEVCAP (sec 9.5).
+	 * Therefore, we can't use pcie_flr(), which checks the VF DEVCAP.
+	 */
+
 	if (probe)
 		return 0;
 
-	pcie_capability_write_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR);
+	/* Wait for Transaction Pending bit clean */
+	for (i = 0; i < 4; i++) {
+		if (i)
+			msleep((1 << (i - 1)) * 100);
+
+		pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &status);
+		if (!(status & PCI_EXP_DEVSTA_TRPND))
+			goto clear;
+	}
+
+	dev_err(&dev->dev, "transaction is not cleared; "
+			"proceeding with reset anyway\n");
+
+clear:
+	pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR);
+
 	msleep(100);
 
 	return 0;