tree 8af40a878618572e51f4c0a3fc1dfbce028aa202
parent 8b7b6afaa84708d08139daa08538ca3e56c351f1
author Stefan Richter <stefanr@s5r6.in-berlin.de> 1232474998 +0100
committer Stefan Richter <stefanr@s5r6.in-berlin.de> 1232792248 +0100

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>