Messages in this thread | | | Date | Tue, 13 May 2003 16:17:48 -0400 (EDT) | From | Bill Davidsen <> | Subject | Re: 2.5.69 Interrupt Latency |
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On 13 May 2003, Paul Fulghum wrote:
> 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.
Instead of trying to guess when to do it, could the sleep be replaced by setting a flag bit to indicate that a sleep was needed before using the hardware? Then the sleep could be done when needed but no noise on the USB bus wouldn't hurt.
1 - there may be many places, I thought of that but didn't look since someone will tell me if it's a problem.
2 - if you don't use USB why not just take the driver out?
It would be nice to prevent the problem, of course.
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
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