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Date:      Thu, 6 May 2004 11:37:51 -0500 (CDT)
From:      Mike Silbersack <silby@silby.com>
To:        Nate Lawson <nate@root.org>
Cc:        acpi@freebsd.org
Subject:   Re: power savings and usb
Message-ID:  <20040506113610.D2198@odysseus.silby.com>
In-Reply-To: <20040506084132.L41848@root.org>
References:  <200405052004.i45K4EnF029671@repoman.freebsd.org> <20040505171634.N37631@root.org> <20040506025051.V630@odysseus.silby.com> <20040506034307.M811@odysseus.silby.com> <20040506084132.L41848@root.org>

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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



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