The problem could be reproduced with any kernel (tested 3.0.0 so far). Due to
lack of AMD C1E idle accounting in kernel latency requirements cannot be
enforced if needed (via pm_qos for instance) and apparently there are drivers
that don't function correctly with the latencies added by AMD C1E, bttv is an
example. There are also some wireless and sound drivers that might need c1e be
disabled for their proper operation.
Of course a straightforward solution is to disable C1E in the BIOS or use
idle=mwait kernel parameter. But why should the CPU use more power (and reduce
battery life in case of a laptop) when C1E could just be disabled for the short
moments if really needed.
The patch works for me, but someone with more knowledge about ACPI could point
out where to read from the real latency value of C1E (for the time being it's
on/off solution).
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/509219
Title:
bttv driver latency issues with AMD C1E enabled
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