> ACPI defines processor power-saving states C0, C1, C2 and C3. We cannot
> enter C3 if there is busmastering activity, and so we check BM_STS. If this
> is high when it should not be, and we are therefore not using C3, we are
> losing battery life.
USB causes continuous bus mastering.
> 1. The controller is not in Global Suspend
> 2. At least one of the controller's ports is not suspended
> 3. The USB RUN bit is set"
>
> So, which of these three conditions is true, and does it have to be? We also
> see this behavior on Windows 2000, but only when a device is plugged in
> (invoking condition 2, I guess...)
I suspect the win2k folks are polling the USB much less than the normal
1Khz rate when the bus was seen to be empty. I guess we could do similar in
that case.
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