linux/Documentation/video4linux/bttv/README.freeze
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   1
   2If the box freezes hard with bttv ...
   3=====================================
   4
   5It might be a bttv driver bug.  It also might be bad hardware.  It also
   6might be something else ...
   7
   8Just mailing me "bttv freezes" isn't going to help much.  This README
   9has a few hints how you can help to pin down the problem.
  10
  11
  12bttv bugs
  13---------
  14
  15If some version works and another doesn't it is likely to be a driver
  16bug.  It is very helpful if you can tell where exactly it broke
  17(i.e. the last working and the first broken version).
  18
  19With a hard freeze you probably doesn't find anything in the logfiles.
  20The only way to capture any kernel messages is to hook up a serial
  21console and let some terminal application log the messages.  /me uses
  22screen.  See Documentation/serial-console.txt for details on setting
  23up a serial console.
  24
  25Read Documentation/oops-tracing.txt to learn how to get any useful
  26information out of a register+stack dump printed by the kernel on
  27protection faults (so-called "kernel oops").
  28
  29If you run into some kind of deadlock, you can try to dump a call trace
  30for each process using sysrq-t (see Documentation/sysrq.txt).
  31This way it is possible to figure where *exactly* some process in "D"
  32state is stuck.
  33
  34I've seen reports that bttv 0.7.x crashes whereas 0.8.x works rock solid
  35for some people.  Thus probably a small buglet left somewhere in bttv
  360.7.x.  I have no idea where exactly, it works stable for me and a lot of
  37other people.  But in case you have problems with the 0.7.x versions you
  38can give 0.8.x a try ...
  39
  40
  41hardware bugs
  42-------------
  43
  44Some hardware can't deal with PCI-PCI transfers (i.e. grabber => vga).
  45Sometimes problems show up with bttv just because of the high load on
  46the PCI bus. The bt848/878 chips have a few workarounds for known
  47incompatibilities, see README.quirks.
  48
  49Some folks report that increasing the pci latency helps too,
  50althrought I'm not sure whenever this really fixes the problems or
  51only makes it less likely to happen.  Both bttv and btaudio have a
  52insmod option to set the PCI latency of the device.
  53
  54Some mainboard have problems to deal correctly with multiple devices
  55doing DMA at the same time.  bttv + ide seems to cause this sometimes,
  56if this is the case you likely see freezes only with video and hard disk
  57access at the same time.  Updating the IDE driver to get the latest and
  58greatest workarounds for hardware bugs might fix these problems.
  59
  60
  61other
  62-----
  63
  64If you use some binary-only yunk (like nvidia module) try to reproduce
  65the problem without.
  66
  67IRQ sharing is known to cause problems in some cases.  It works just
  68fine in theory and many configurations.  Neverless it might be worth a
  69try to shuffle around the PCI cards to give bttv another IRQ or make
  70it share the IRQ with some other piece of hardware.  IRQ sharing with
  71VGA cards seems to cause trouble sometimes.  I've also seen funny
  72effects with bttv sharing the IRQ with the ACPI bridge (and
  73apci-enabled kernel).
  74
  75
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