Re: broken bm_sts on 82801CA?

[Ducrot Bruno <ducrot-kk6yZipjEM5g9hUCZPvPmw@public.gmane.org>]

On Wed, Oct 08, 2003 at 09:55:35AM -0700, Nate Lawson wrote:
> On Wed, 8 Oct 2003, Ducrot Bruno wrote:
> > On Tue, Oct 07, 2003 at 11:10:37AM -0700, Nate Lawson wrote:
> > > On Tue, 7 Oct 2003, Ducrot Bruno wrote:
> > > > On Mon, Oct 06, 2003 at 11:38:07PM -0700, Nate Lawson wrote:
> > > > > My chipset claims to be: Intel 82801CA/CAM (ICH3) and it's on an IBM T23
> > > > > thinkpad.  While testing my Cx driver, I noticed that bm_sts is always
> > > > > set, even when I clear it by writing a 1 to the register.  I _know_ the
> > > > > box is idle so I believe this bit to be broken.  Can anyone confirm this?
> > > > > I noticed the errata probe for the PIIX4 but I don't think it covers my
> > > > > part.
> > > >
> > > > Have you any kind of usb bus support compiled in your kernel?
> > > > If yes, try without.
> > >
> > > Ah, I'll try that.  I do have USB support compiled in.  This is on
> > > FreeBSD, btw.
> >
> > That more an hardware design issue due to how hotplug work in usb busses
> > in general, and it may need to be workaround, so if anybody haven't yet worked on
> > C-states on FreeBSD..  Please note also that Linux do not workaround that
> > btw.
> 
> I have implemented C-states in freebsd, that's how I ran into this
> problem.  I'll be committing the code once it's cleaned up a little.
> 
> Since Linux always demotes to "don't enter a Cx state" if bm_sts indicates
> activity, are you saying that if you have a USB bus configured in Linux,
> you don't even use C1 (HLT)?
> 

What?  If so, there is a bug somewhere since we should look at bm status only at
C2 (only if we have to go to C3) or C3 state.
Sound like you are right, btw.  I have to look a little deeper.  Thanks for pointing
this.

-- 
Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.


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