Commit 8b7b6afa authored by Stefan Richter's avatar Stefan Richter
Browse files

firewire: ohci: 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

 .

In a quick test with a JVC camcorder (which didn't malfunction like the
reported camcorders), this change decreased the number of ack_busy_X
from 16 in three runs of dvgrab to 4 in three runs of the same capture
duration.
Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent b0068549
......@@ -226,7 +226,7 @@ static inline struct fw_ohci *fw_ohci(struct fw_card *card)
#define CONTEXT_DEAD 0x0800
#define CONTEXT_ACTIVE 0x0400
#define OHCI1394_MAX_AT_REQ_RETRIES 0x2
#define OHCI1394_MAX_AT_REQ_RETRIES 0xf
#define OHCI1394_MAX_AT_RESP_RETRIES 0x2
#define OHCI1394_MAX_PHYS_RESP_RETRIES 0x8
......
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