[linux-dvb] CX18 Oops

Andy Walls awalls at radix.net
Tue Aug 19 01:52:19 CEST 2008


On Mon, 2008-08-18 at 06:35 -0400, Brandon Jenkins wrote:
> On Sat, Aug 16, 2008 at 10:13 PM, Andy Walls <awalls at radix.net> wrote:
> > On Mon, 2008-08-11 at 17:33 -0400, Brandon Jenkins wrote:
> >> On Fri, Aug 8, 2008 at 10:18 AM, Andy Walls <awalls at radix.net> wrote:
> >> > Brandon,
> >> >
> >> > I have checked in a fix to defend against the Ooops we both encountered.
> >> > The fix will also generate a WARN dump and some queue stats when it runs
> >> > across the cause, but will otherwise try to clean up as best it can to
> >> > allow further operation.
> >> >
> >> > The band-aid fix is the latest change at
> >> >
> >> > http://linuxtv.org/hg/~awalls/v4l-dvb
> >> >
> >> > Please provide the extra debug that happens if you encounter the warning
> >> > in your logs.  I have only encountered the problem twice over a several
> >> > month period, so its hard to get insight into the root cause buffer
> >> > accounting error at that rate.
> >>
> >> Andy,
> >>
> >> I had an oops today, first one in a few days
> >>
> >> Brandon
> >
> > Brandon & Jeff,
> >
> > I have updated my repo at
> >
> > http://linuxtv.org/hg/~awalls/v4l-dvb
> >
> > with 3 changes:
> >
> > 1. Back out the original band aid fix
> > 2. Simplify the queue flush routines (you will not see that oops again)
> > 3. Fix the interrupt handler to obtain a queue lock (prevents queue
> > corruption)
> >
> > >From most of the output you provided, it was pretty obvious that q_full
> > was always claiming to have more buffers that it actually did.  I
> > hypothesized this could come about at the end of a capture when the
> > encoder hadn't really stopped transferring buffers yet (after we told it
> > to stop) and then we try to clear q_full while the interrupt handler is
> > still trying to add buffers.  This could happen because the interrupt
> > handler never (ever) properly obtained a lock for manipulating the
> > queues.  This could have been causing the queue corruption.
> >
> > Please test.  I need feedback that I haven't introduced a deadlock.
> >
> > It also appears that the last change requiring the interrupt handler to
> > obtain a lock, completely mitigates me having to use the "-cache 8192"
> > option to mplayer for digital captures, and greatly reduces the amount
> > of cache I need to have mplayer use for analog captures.
> >
> [snip]
> 
> Andy,
> 
> I have update to the new code. Interestingly now I am getting audio
> noises (chirping) while watching TV.

Analog or digital capture?  Analog tuner only or analog line in as well?
All digitial channels or just certain ones?


> Is there anything which has been done that could affect sound?

For analog capture, I recently added code to "lock" the video PLL to the
audio PLL in the cx18-av core.  The Conexant CX2854[0123] data sheet
recommended this for MPEG encoding applications - a primary use case for
the CX23418.

In cx18-av-audio.c:set_audclk_freq(), look for lines like

	cx18_av_write4(cx, 0x128, 0xa1nnnnnn);

and change them to 

	cx18_av_write4(cx, 0x128, 0xa0nnnnnn);

to have the video and audio sample clocks run independently again and
effectively back out that change.


You can also try to back out the change to have the interrupt handler
obtain the qlock spinlock.  It's the wrong thing to do, but it will let
you determine if it causes the artifacts you now hear.


If that doesn't make the chirping go away, then:

does caching help?  Does recordings captured with "cat" exhibit the
chirps on playback? Does mplayer (64 bit native) exhibit the chirping as
well as Sage (32 bit compat mode)?



> Otherwise no issues thus far.

:)

I won't have access to personal email for the next few days, so I won't
be able to help until Friday at the earliest.

Regards,
Andy

> Brandon





More information about the linux-dvb mailing list