[FFADO-devel] Meaning of cycletimer / CTR counter messages

[Jonathan W. <jw...@ph...>]

Hi Pieter

Over on the ffado-users list (in the "MOTU Ultralite" thread) I'm trying to
work out why a few users don't seem to be able to get reliable streaming. 
Since I know you're busy (and because this is more a developer issue than a
user one) I've distilled the questions I have for you here in case it's
easier for you to deal with right now.

The system's firewire chipset is reported as this:

   0a:09.0 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller (rev 05) 

Do you know off-hand whether this is one of the "bad" ones?

[ As an aside, we probably need to collect all the "known bad" chipsets 
(and maybe the "known good" as well) and put them on the web.  I might see
if I can start something in the next few weeks if no one else does it first.
This would help immensely in situations like this. ]

On this particular system things seem to start OK (and audio is produced),
but after a short period of time we see a series of messages like this:

  getPacket: reconstructed CTR counter discrepancy
  :
  getPacket:  diffcy = -111
  waitForPeriod:  wait extended since period not ready...
  getPacket: (0x1915ff0) OHCI issue on cycle 7055 (dropped_cycles=0,
    last_cycle=7055, dropped=1, skipped: 0)
  getPacket: reconstructed CTR counter discrepancy
  :
  getPacket:  diffcy = -110
  :
  getPacket:  diffcy = -109

jackd then closes down in response to an xrun.

Is this the signature of an infamous "dropped packet" (suggested by the
"OHCI issue" message) - and therefore a bad firewire chipset?  Or is it
something more beneign like USB shared interrupts, or not having a "low
latency desktop" kernel?

What exactly does the "reconstructed CTR counter discrepancy" message mean?

>From another user (to whom I haven't replied yet) I'm seeing messages like

  Execute: (0x8071cf8) have to retry CTR read, diff unrealistic

from CycleTimerHelper.cpp)[ 389].  Is this anything to worry about?  This
system uses an on-board SiS firewire chipset - do we have any experience
with those?

Regards
  jonathan