[mythtv-users] Firewire Issues

DISAFAN disafan at aim.com
Wed Oct 10 22:11:00 UTC 2007

Yes, well, I searched the user list, as I'm not a developer. But it does answer my question. I wish I was, but my programming skills were never at that high a level. And the kernel issue you mention is one I've been experiencing with DMA. I look forward to the patch making it into a future kernel. Keep me posted or send me a URL to the filed report so I can monitor its status. I probably should break down and break out the kernel source...but I admit I probably won't for now.

From: Bruce Markey <bjm at lvcm.com>
Subject: Re: [mythtv-users] Firewire Issues
To: Discussion about mythtv <mythtv-users at mythtv.org>
Message-ID: <470D2039.4060902 at lvcm.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

DISAFAN wrote:

> > I confess, I am suffering from a lack of understanding of how to proceed 
> > on my firewire issues. Positively, all of the analog channels...the 
> > basic cable stuff...seems to come through on my SA3250HD. The HD 
> > channels seem to come through. The digital versions of the analog feed 
> > aren't tuning...but I figure if I can get rid of the PVR-150 hooked into 
> > the box output, it will allow me to free up a PCI slot for another QAM 
> > tuner.
> > 
> > That said, my firewire recording, like many peoples, is inconsistent. 
> > When it records, it records. When it doesn't, it doesn't, and I have to 
> > stop MythTV, reset the firewire bus, and that seems to clear the problem.
> > 
> > I have high hopes a future bugfix will stabilize the connection...it 

Wed, 18 Jul 2007 is actually in the past. If you are using a 64
bit kernel, there is a bug that causes a memory error which make
recording and firewire_tester appear to fail due to a connection
problem. However, it is a kernel memory error and the connection
is actually okay. "grep dma_region_alloc /var/log/syslog".

: root at bigboy \# ; zcat /var/log/syslog.4.gz | grep dma_region_alloc
Oct  3 21:54:54 bigboy kernel:  [<ffffffff880652c7>] :ieee1394:dma_region_alloc+0x37/0x126
Oct  3 21:54:54 bigboy kernel: dma_region_alloc: vmalloc_32() failed
Oct  3 21:54:56 bigboy kernel:  [<ffffffff880652c7>] :ieee1394:dma_region_alloc+0x37/0x126

I had to go back in my logs to find these as they haven't happened
since I applied this patch the evening of Oct 3:


Since booting the patched kernel, I have never had one firewire
recording fail. I need to run "firewire_tester -p -n 0 -R" once
after rebooting then the connection stays good until the next
reboot (the memory bug would make firewire_tester give a false
negative but most likely the connection was always good).


> > I have searched through the archives and seem no closer to a best 
> > solution, so I decided to seek commentary.

You missed the dev list thread "LFireDev Error: Starting A/V
streaming: Cannot allocate memory". I'm lining up my ducks
to submit a complete and proper bug report for kernel.org so
this can be fixed without patching in future kernels.

--  bjm

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