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SubjectRe: 2.4.22 USB problem (uhci)
On Fri, Sep 19, 2003 at 02:14:49PM -0700, Jan Rychter wrote:
> >>>>> "Greg" == Greg KH <> writes:
> Greg> On Fri, Sep 19, 2003 at 01:29:55PM -0700, Jan Rychter wrote: If
> Greg> you want to suspend using 2.4, unload the usb drivers entirely.
> Greg> That's the only safe way.
> >>
> >> I wasn't talking about suspending, but about processor
> >> C-states. These are power states that the mobile processors enter
> >> dynamically, many times a second. In my case:
> Greg> Ah, sorry. I'm getting D and C states mixed up here.
> [...]
> You probably mean S-states, which are for sleep.

Ugh, ok, I give up :)

> >> As you can see, C3 (lowest power) is being used a lot. This makes my
> >> laptop run cool. If I use usb-uhci, the processor is never able to
> >> go into C3 because of DMA activity. uhci is better, because it at
> >> least permits me to use C3 when there are no devices plugged in.
> >>
> >> And going back to the uhci problem... ?
> Greg> UHCI by design sucks massive PCI bandwidth. There is logic in
> Greg> the uhci drivers that try to help this out by reducing
> Greg> transactions when not much is going on, but there's only so much
> Greg> we can do in software, sorry. I'm guessing that you aren't going
> Greg> to be able to change this.
> Greg> Unless you go buy a ohci usb cardbus controller card :)
> Now you've confused me.
> Do your comments above apply to "uhci" or "usb-uhci"?
> Please allow me to restate the original problem:
> -- I usually use uhci instead of usb-uhci, because it is able to go
> into "suspend mode" when no devices are plugged, which allows the
> CPU to enter C3 states,
> -- usb-uhci eats CPU power by keeping it in C2 constantly because of
> busmastering DMA activity, therefore being much less useful,
> -- uhci generally works for me just fine, but breaks in one particular
> case, when removing the device causes a strange message to be
> printed and the system being unable to use the C3 states again,
> until uhci is unloaded and reloaded back again.
> Just as a reminder, this message is:
> uhci.c: efe0: host controller halted. very bad
> I hope if the message says "very bad", then this is something that can
> be fixed. I was therefore reporting a problem with "uhci" and kindly
> asking for help.

Ok, sorry for the confusion. No I don't know of a fix for this problem,
but one just went into the 2.6 kernel tree for the uhci-hcd driver that
you might want to take a look at that fixed a problem almost exactly
like this.


greg k-h
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