ieee1394: ohci1394: increase AT req. retries, fix ack_busy_X from Panasonic camcorder...
authorStefan Richter <stefanr@s5r6.in-berlin.de>
Tue, 20 Jan 2009 18:09:58 +0000 (19:09 +0100)
committerStefan Richter <stefanr@s5r6.in-berlin.de>
Sat, 24 Jan 2009 10:17:28 +0000 (11:17 +0100)
commit64c634ef83991b390ec0503e61f16efb0ba3c60b
tree8af40a878618572e51f4c0a3fc1dfbce028aa202
parent8b7b6afaa84708d08139daa08538ca3e56c351f1
ieee1394: ohci1394: increase AT req. retries, fix ack_busy_X from Panasonic camcorders and others

Camcorders have a tendency to fail read requests to their config ROM and
write request to their FCP command register with ack_busy_X.  This has
become a problem with newer kernels and especially Panasonic camcorders,
causing AV/C in dvgrab and kino to fail.  Dvgrab for example frequently
logs "send oops"; kino reports loss of AV/C control.  I suspect that
lower CPU scheduling latencies in newer kernels made this issue more
prominent now.

According to
https://sourceforge.net/tracker/?func=detail&atid=114103&aid=2492640&group_id=14103
this can be fixed by configuring the FireWire controller for more
hardware retries for request transmission; these retries are evidently
more successful than libavc1394's own retry loop (typically 3 tries on
top of hardware retries).

Presumably the same issue has been reported at
https://bugzilla.redhat.com/show_bug.cgi?id=449252 and
https://bugzilla.redhat.com/show_bug.cgi?id=477279 .

Tested-by: Mathias Beilstein
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
drivers/ieee1394/ohci1394.h