From owner-freebsd-arch@FreeBSD.ORG  Wed Mar 19 16:23:24 2008
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Date: Wed, 19 Mar 2008 10:21:49 -0600 (MDT)
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To: jhb@FreeBSD.org
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: bzeeb-lists@lists.zabbadoz.net, phk@phk.freebsd.dk, arch@FreeBSD.org,
	freebsd-arch@FreeBSD.org
Subject: Re: Power-Mgt
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In message: <200803190854.39131.jhb@freebsd.org>
            John Baldwin <jhb@freebsd.org> writes:
: On Wednesday 19 March 2008 07:29:43 am Poul-Henning Kamp wrote:
: > In message <20080319.051604.63052713.imp@bsdimp.com>, "M. Warner Losh" 
: writes:
: > >In message: <20080318085804.I50685@maildrop.int.zabbadoz.net>
: > >
: > >            "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> writes:
: > >: what actually happens to an unrecognized card or a card with no driver
: > >: loaded currently? How much power does an unsued card use and can we do
: > >: anything about that? Are we perhaps already doing something about
: > >: that?
: > >
: > >For PCI it is set into D3 state.  Or at least was until this caused a
: > >problem with some raid controllers that didn't follow the rules and
: > >had extra devices that the card used, but that the OS didn't have a
: > >driver for.
: > >
: > >For PC Card, the card is powered down entirely.  For CardBus I think
: > >the same.  For USB, ugen takes it, and therefore it is powered up.
: >
: > Not to mention this comment from acpi_cpu.c:
: >
: >     /*
: >      * Check for bus master activity.  If there was activity, clear
: >      * the bit and use the lowest non-C3 state.  Note that the USB
: >      * driver polling for new devices keeps this bit set all the
: >      * time if USB is loaded.
: >      */
: 
: That is something to be fixed in the USB driver, but yes.  Changing the USB 
: driver to power down when nothing is plugged in may help.

hps' usb stack implements something in this area.

Warner