Am 15.11.2011 19:43, schrieb Pitt, Jason N:
I have a bunch of usb cards that have moschip ehci controllers in them that
have a silicon bug that causes the microframe counter to be updated before the
frame counter here's the details of the patch:
This patch (as1489) works around a hardware bug in MosChip EHCI
controllers. Evidently when one of these controllers increments the
frame-index register, it changes the three low-order bits (the
microframe counter) before changing the higher order bits (the frame
counter). If the register is read at just the wrong time, the value
obtained is too low by 8.
When the appropriate quirk flag is set, we work around this problem by
reading the frame-index register a second time if the first value's
three low-order bits are all 0. This gives the hardware a chance to
finish updating the register, yielding the correct value.
This prevents the main problem of the driver crashing but there is a lingering issue that
I believe is due to the uvcvideo driver's handling of the patch. The video stream
eventually seems to "loose sync" is the best way i can describe it....I've
posted a video of the problem on youtube here: http://www.youtube.com/watch?v=W-gAHa0zL7A
There are 12 instances of guvcvideo running, 3 or 4 of the cameras have
developed the issue after about 12 hours. When the glitch happens, the bottom
portion of the image freezes and the flashing segments at the top are still
updating but clearly something is messed up. Any thoughts?
The problem in this case is to run uvcvideo trace for 12 hours :)
can you try to run it again and enable trace for short time with correct
image and with brocken image.
you do not need reloading module to do that. Do fallowing:
sudo echo 0xffff > /sys/module/uvcvideo/parameters/trace &&
sleep 10s &&
sudo echo 0 > /sys/module/uvcvideo/parameters/trace
Regards,
Alexey
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