Date: Thu, 26 Aug 2004 12:48:48 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: nate@root.org Cc: acpi@freebsd.org Subject: Re: Cx states not working on Dell Inspiron 8600 (Pentium M) Message-ID: <20040826.124848.93209661.imp@bsdimp.com> In-Reply-To: <412E2D33.1090900@root.org> References: <20040826163734.49EBF5D04@ptavv.es.net> <20040826181008.GA792@galgenberg.net> <412E2D33.1090900@root.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message: <412E2D33.1090900@root.org>
Nate Lawson <nate@root.org> writes:
: Ulrich Spoerlein wrote:
: > On Thu, 26.08.2004 at 09:37:33 -0700, Kevin Oberman wrote:
: >
: >>The cx_usage is limited to C1 or C2 if USB is loaded. It's polling of
: >>the bus for changes prevents the state from dropping to anything really
: >>useful. If you don't always need USB, build a kernel without it and load
: >>it as required.
: >
: > Ah, that explains it then. Is there anything that can be done about
: > that? Does that mean, that even Windows is not using C3 and C4 if there
: > is a USB mouse plugged in?
:
: USB needs to be improved to poll more delicately. I don't intend to
: work on this any time soon but it's on the acpi todo list:
:
: http://www.root.org/~nate/
This strikes me as something more properly belonging to the busdma
layer. When there's bus mastering active, then we can't go into
C3/C4. However, not all drivers in the tree are good about only
loading the DMA maps when a DMA is possible (but leaving it active all
the time, say), so maybe there's some wider-ranging problems that need
to be looked at as well. While USB may also need some work to be
better about when it does DMA, I suspect that the problem is larger
than USB... Why does the bus mastering that ATA does not a problem
while USB's is a problem?
Have you isolaged the USB agressive polling problem to some code I can
look at. I have some usb code staring time on my plate for work and
it would be nice to know where to look.
Warner
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040826.124848.93209661.imp>