[linux-dvb] dvb-bt8xx FDSR IRQ lockup

[Hamish Moffatt <hamish@cloud.net.au>]

Hi,

I've been having some trouble lately with my Avermedia 761. I get some
FDSR interrupts in the log, followed by an INT lockup message.

Sep  5 12:48:10 tv kernel: bt878(0): irq FDSR risc_pc=1f96e210
Sep  5 12:48:10 tv last message repeated 418 times
Sep  5 12:48:10 tv kernel: bt878(0): IRQ lockup, cleared int mask

FDSR means "FIFO Data Resynchronization occurred. The number of pixels,
lines or modes passing through FIFO does not match RISC program
expectations." according to the BT878A data sheet.

I think this is caused by buffer overflows due to PCI latency, but I'm
not sure. I have seen FBUS errors in the past, which the data sheet
describes as "Set when a pixel data FIFO overrun condition is being
handled by dropping as many DWORDs as needed, indicating bus access 
latencies are long.", but I don't always get those.

After the interrupt storm happens (and IRQ lockup is logged), I get no
more data from the card ever, until I remove/reload the driver (or
reboot).

I think these problems started occurring when I last upgraded MythTV and
changed my configuration a little, but that shouldn't have made much
difference except increasing CPU load a bit possibly. It might have also
increased the traffic to the AGP card, but I believe that is a separate
bus (and therefore wouldn't increase PCI latency).

The log above resulted when I tried to watch Myth's "live TV", which is
for the first time in days. I have been recording things without issue
for the past > 2 weeks.

I'm running kernel 2.6.7. Is there any way this condition could be
better handled, eg have the driver reset the hardware when this occurs,
rather than needing to reload the driver manually?

I've already fiddled with setpci and made the condition a bit rarer, but
the only thing on the same PCI bus is the other DVB card (idle when the
error occurred) and an old NIC (also idle). So I can't see what it's
competing for.

Any thoughts?

thanks,
Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>