firewire: ohci: work around VIA and NEC PHY packet reception bug

Stefan Richter · Stefan Richter · commit a4dc090b6cb4 · 2010-08-29T09:17:31.000+02:00
VIA VT6306, VIA VT6308, and NEC OrangeLink controllers do not write
packet event codes for received PHY packets (or perhaps write
evt_no_status, hard to tell).  Work around it by overwriting the
packet's ACK by ack_complete, so that upper layers that listen to PHY
packet reception get to see these packets.

(Also tested:  TI TSB82AA2, TI TSB43AB22/A, TI XIO2213A, Agere FW643,
JMicron JMB381 --- these do not exhibit this bug.)

Clemens proposed a quirks flag for that, IOW whitelist known misbehaving
controllers for this workaround.  Though to me it seems harmless enough
to enable for all controllers.

The log_ar_at_event() debug log will continue to show the original
status from the DMA unit.

Reported-by: Clemens Ladisch &lt;clemens@ladisch.de&gt; (VT6308)
Signed-off-by: Stefan Richter &lt;stefanr@s5r6.in-berlin.de&gt;
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
@@ -694,7 +694,15 @@ static __le32 *handle_ar_packet(struct ar_context *ctx, __le32 *buffer)
 	log_ar_at_event('R', p.speed, p.header, evt);
 
 	/*
-	 * The OHCI bus reset handler synthesizes a phy packet with
+	 * Several controllers, notably from NEC and VIA, forget to
+	 * write ack_complete status at PHY packet reception.
+	 */
+	if (evt == OHCI1394_evt_no_status &&
+	    (p.header[0] & 0xff) == (OHCI1394_phy_tcode << 4))
+		p.ack = ACK_COMPLETE;
+
+	/*
+	 * The OHCI bus reset handler synthesizes a PHY packet with
 	 * the new generation number when a bus reset happens (see
 	 * section 8.4.2.3).  This helps us determine when a request
 	 * was received and make sure we send the response in the same
