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

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

[Stefan Richter]

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 <clemens@ladisch.de> (VT6308)
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
 drivers/firewire/ohci.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Index: b/drivers/firewire/ohci.c
===================================================================
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -694,7 +694,15 @@ static __le32 *handle_ar_packet(struct a
 	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

-- 
Stefan Richter
-=====-==-=- =--- ===--
http://arcgraph.de/sr/

[PATCH] firewire: ohci: add some "unlikely" hints

[Stefan Richter]

Mark evt_no_status and evt_bus_reset packet reception events as ones
that occur rarely.

Also, inline the debug flag check of log_ar_at_event().  [The same is
hopefully not necessary for log_irqs() which is only called at a single
site and hence auto-inlined by the compiler.]

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
 drivers/firewire/ohci.c |   28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

Index: b/drivers/firewire/ohci.c
===================================================================
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -398,14 +401,11 @@ static const char *phys[] = {
 	[0x2] = "self-id packet",	[0x3] = "-reserved-",
 };
 
-static void log_ar_at_event(char dir, int speed, u32 *header, int evt)
+static void _ar_at_event(char dir, int speed, u32 *header, int evt)
 {
 	int tcode = header[0] >> 4 & 0xf;
 	char specific[12];
 
-	if (likely(!(param_debug & OHCI_PARAM_DEBUG_AT_AR)))
-		return;
-
 	if (unlikely(evt >= ARRAY_SIZE(evts)))
 			evt = 0x1f;
 
@@ -456,6 +456,12 @@ static void log_ar_at_event(char dir, in
 	}
 }
 
+static inline void log_ar_at_event(char dir, int speed, u32 *header, int evt)
+{
+	if (unlikely(param_debug & OHCI_PARAM_DEBUG_AT_AR))
+		_ar_at_event(dir, speed, header, evt);
+}
+
 #else
 
 #define param_debug 0
@@ -697,7 +703,7 @@ static __le32 *handle_ar_packet(struct a
 	 * Several controllers, notably from NEC and VIA, forget to
 	 * write ack_complete status at PHY packet reception.
 	 */
-	if (evt == OHCI1394_evt_no_status &&
+	if (unlikely(evt == OHCI1394_evt_no_status) &&
 	    (p.header[0] & 0xff) == (OHCI1394_phy_tcode << 4))
 		p.ack = ACK_COMPLETE;
 
@@ -714,7 +720,7 @@ static __le32 *handle_ar_packet(struct a
 	 * wrong generation.  We set the correct generation for these
 	 * at a slightly incorrect time (in bus_reset_tasklet).
 	 */
-	if (evt == OHCI1394_evt_bus_reset) {
+	if (unlikely(evt == OHCI1394_evt_bus_reset)) {
 		if (!(ohci->quirks & QUIRK_RESET_PACKET))
 			ohci->request_generation = (p.header[2] >> 16) & 0xff;
 	} else if (ctx == &ohci->ar_request_ctx) {

-- 
Stefan Richter
-=====-==-=- =--- ===--
http://arcgraph.de/sr/