Power-Mgt

[John Baldwin]

On Wednesday 19 March 2008 07:29:43 am Poul-Henning Kamp wrote:
> In message <20080319.051604.63052713.imp at bsdimp.com>, "M. Warner Losh" 
writes:
> >In message: <20080318085804.I50685 at maildrop.int.zabbadoz.net>
> >
> >            "Bjoern A. Zeeb" <bzeeb-lists at 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.

-- 
John Baldwin