firewire: ohci: Make cycleMatch ISO transmission work

Calling the START_ISO ioctl with a nonnegative cycle paramater has
never worked.  Last night I got around to figuring out why.  Most of
this patch is a big comment explaining why we enable an interrupt
source then don't actually do anything when we get one.  As the
comment says, we should do more, but we don't have a way to tell
userspace what happened. . .

Signed-off-by: Jay Fenlason <fenlason@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (edited comment)

drivers/firewire/ohci.c

@@ -275,7 +275,7 @@ static void log_irqs(u32 evt)
 	    !(evt & OHCI1394_busReset))
 		return;
 
-	fw_notify("IRQ %08x%s%s%s%s%s%s%s%s%s%s%s%s%s\n", evt,
+	fw_notify("IRQ %08x%s%s%s%s%s%s%s%s%s%s%s%s%s%s\n", evt,
 	    evt & OHCI1394_selfIDComplete	? " selfID"		: "",
 	    evt & OHCI1394_RQPkt		? " AR_req"		: "",
 	    evt & OHCI1394_RSPkt		? " AR_resp"		: "",
@@ -286,6 +286,7 @@ static void log_irqs(u32 evt)
 	    evt & OHCI1394_postedWriteErr	? " postedWriteErr"	: "",
 	    evt & OHCI1394_cycleTooLong		? " cycleTooLong"	: "",
 	    evt & OHCI1394_cycle64Seconds	? " cycle64Seconds"	: "",
+	    evt & OHCI1394_cycleInconsistent	? " cycleInconsistent"	: "",
 	    evt & OHCI1394_regAccessFail	? " regAccessFail"	: "",
 	    evt & OHCI1394_busReset		? " busReset"		: "",
 	    evt & ~(OHCI1394_selfIDComplete | OHCI1394_RQPkt |
@@ -293,6 +294,7 @@ static void log_irqs(u32 evt)
 		    OHCI1394_respTxComplete | OHCI1394_isochRx |
 		    OHCI1394_isochTx | OHCI1394_postedWriteErr |
 		    OHCI1394_cycleTooLong | OHCI1394_cycle64Seconds |
+		    OHCI1394_cycleInconsistent |
 		    OHCI1394_regAccessFail | OHCI1394_busReset)
 						? " ?"			: "");
 }
@@ -1439,6 +1441,17 @@ static irqreturn_t irq_handler(int irq, void *data)
 			  OHCI1394_LinkControl_cycleMaster);
 	}
 
+	if (unlikely(event & OHCI1394_cycleInconsistent)) {
+		/*
+		 * We need to clear this event bit in order to make
+		 * cycleMatch isochronous I/O work.  In theory we should
+		 * stop active cycleMatch iso contexts now and restart
+		 * them at least two cycles later.  (FIXME?)
+		 */
+		if (printk_ratelimit())
+			fw_notify("isochronous cycle inconsistent\n");
+	}
+
 	if (event & OHCI1394_cycle64Seconds) {
 		cycle_time = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
 		if ((cycle_time & 0x80000000) == 0)
@@ -1528,6 +1541,7 @@ static int ohci_enable(struct fw_card *card, u32 *config_rom, size_t length)
 		  OHCI1394_reqTxComplete | OHCI1394_respTxComplete |
 		  OHCI1394_isochRx | OHCI1394_isochTx |
 		  OHCI1394_postedWriteErr | OHCI1394_cycleTooLong |
+		  OHCI1394_cycleInconsistent |
 		  OHCI1394_cycle64Seconds | OHCI1394_regAccessFail |
 		  OHCI1394_masterIntEnable);
 	if (param_debug & OHCI_PARAM_DEBUG_BUSRESETS)