firewire: fw-ohci: make sure HCControl register LPS bit is set

I've now witnessed multiple occasions where one of my controllers (a very
poorly working JMicron PCIe card) fails to get its registers properly set
up in ohci_enable(), apparently due to an occasionally very slow to
initiate SClk. The easy fix for this problem is to add a tiny while loop
to try again a time or three after initially enabling LPS before we
move on (or give up).

Of course, the card still isn't fully functional yet, but this gets it at
least one tiny step closer...
Signed-off-by: Jarod Wilson <jwilson@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-ohci.c

@@ -1390,6 +1390,8 @@ static int ohci_enable(struct fw_card *card, u32 *config_rom, size_t length)
 {
 	struct fw_ohci *ohci = fw_ohci(card);
 	struct pci_dev *dev = to_pci_dev(card->device);
+	u32 lps;
+	int i;
 
 	if (software_reset(ohci)) {
 		fw_error("Failed to reset ohci card.\n");
@@ -1401,13 +1403,24 @@ static int ohci_enable(struct fw_card *card, u32 *config_rom, size_t length)
 	 * most of the registers.  In fact, on some cards (ALI M5251),
 	 * accessing registers in the SClk domain without LPS enabled
 	 * will lock up the machine.  Wait 50msec to make sure we have
-	 * full link enabled.
+	 * full link enabled.  However, with some cards (well, at least
+	 * a JMicron PCIe card), we have to try again sometimes.
 	 */
 	reg_write(ohci, OHCI1394_HCControlSet,
 		  OHCI1394_HCControl_LPS |
 		  OHCI1394_HCControl_postedWriteEnable);
 	flush_writes(ohci);
-	msleep(50);
+
+	for (lps = 0, i = 0; !lps && i < 3; i++) {
+		msleep(50);
+		lps = reg_read(ohci, OHCI1394_HCControlSet) &
+		      OHCI1394_HCControl_LPS;
+	}
+
+	if (!lps) {
+		fw_error("Failed to set Link Power Status\n");
+		return -EIO;
+	}
 
 	reg_write(ohci, OHCI1394_HCControlClear,
 		  OHCI1394_HCControl_noByteSwapData);