power savings and usb

[Mike Silbersack]

On Thu, 6 May 2004, Nate Lawson wrote:

> > Gah, except that my experiment in clockswitching made the usb stack mad,
> > so it's constantly priniting "usb0: X scheduling overruns", where X
> > appears to be a number containing one or two bits of entropy per second.
> > I will have to go visit ohci.c with a cluebat when I get a chance.
> >
> > Er, it stopped when I plugged in the power cord, and starts again when I
> > unplugged it.  Is it possible that ohci.c is reading some USB voltage
> > value instead of the overrun bit that it thinks it is reading?
>
> hw.acpi.cpu.cx_supported: C1/0 C2/84 C3/120
> hw.acpi.cpu.cx_lowest: 1
> hw.acpi.cpu.cx_history: 9175/0 173443/9175 0/0
>
> This means I am requesting a lowest sleep of C2 (idx 1 of the options
> supported).  The history values show that I haven't used C3 at all and am
> using C2 at a rate of about 95%.
>
> ohci may have problems with C3.  On my uhci, it demotes to C2 without
> causing problems.  You can override this by setting in /etc/rc.conf:
>
> economy_cx_lowest="1"
>
> -Nate

Something else must be happening, because:

hw.acpi.cpu.cx_supported: C1/1 C2/99 C3/288
hw.acpi.cpu.cx_lowest: 0
hw.acpi.cpu.cx_history: 5558639/0 0/0 0/0

But, since I went and killed the scheduling overrun interrupts at the
source, we don't need to worry anymore. :)

Mike "Silby" Silbersack