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

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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>
This commit is contained in:
Stefan Richter 2010-08-28 14:21:26 +02:00
parent 2222bcb767
commit a4dc090b6c
1 changed files with 9 additions and 1 deletions
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10
drivers/firewire/ohci.c
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@ -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