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SubjectRe: 2.5.69 Interrupt Latency
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On Tue, 2003-05-13 at 10:26, Alan Stern wrote:

> Putting in a sanity check for the global suspend state will be very easy.
> But I would like to point out that this "global suspend" does not refer to
> the entire system, only the USB bus.

That is a problem then, because the delay can still
occur during normal system operation.

> I'm not sure under what
> circumstances the bus is placed in global suspend; I think it's just when
> there are no devices attached (or the last remaining device is detached).
>
> However, there have been cases on my own system where turning off the only
> USB peripheral caused the driver to bounce between suspend_hc() and
> wakeup_hc() several times without any apparent explanation -- possibly as
> a result of transient electrical signals on the bus (?). So perhaps
> moving that delay out of the ISR isn't such a bad idea.

Agreed. If this can happen on functional USB controllers
when no devices are attached, then it is a serious problem.

--
Paul Fulghum, paulkf@microgate.com
Microgate Corporation, http://www.microgate.com


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