Messages in this thread | | | From | Jan Rychter <> | Subject | Re: 2.4.22 USB problem (uhci) | Date | Sat, 20 Sep 2003 17:15:57 -0700 |
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>>>>> "Jan" == Jan Rychter <jan@rychter.com>: >>>>> "Greg" == Greg KH <greg@kroah.com> writes: Jan> [...]
> 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.
Greg> Ok, sorry for the confusion. No I don't know of a fix for this Greg> problem, but one just went into the 2.6 kernel tree for the Greg> uhci-hcd driver that you might want to take a look at that fixed Greg> a problem almost exactly like this.
Jan> Greg,
Jan> I've looked at uhci.c, the message comes from line 2461, in Jan> uhci_interrupt. But there is no chance I will be able to fix it Jan> without first understanding thoroughly how uhci.c works.
Jan> So I guess this goes into my "unfixed Linux bugs" bin.
I've just realized that some people may not know why the above uhci bug is a problem.
Having done some measurements and calculations, the above uhci bug translates into a shortened battery life: 20 minutes less for the laptop I've been testing on. You get 1h30 instead of 1h50 you would normally get if uhci would work correctly.
That's like having only 84% of your battery available to start with.
--J.
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