On Thu, Jul 17, 2014 at 05:55:22PM +0800, Pratyush Anand wrote:
> Hi David,
>
> On Thu, Jul 17, 2014 at 05:37:44PM +0800, David Laight wrote:
> > From: Pratyush Anand
> > ...
> > > Only side effect of long timeout: If a device was connected before
> > > suspend, and was removed while system was asleep, then the penalty
> > > would be the timeout ie 2000 ms. I do not see a way to handle this. I
> > > can put a FIXME note for this in patch.
> > ...
> >
> > Can't you use the static detection that a device is connected at all?
> > (ie look at whether the USB1/2 D+/D- lines have been pulled up/down).
>
> Unfortunately, there is no way for software(other than CSC bit from
> xhci registers) to know that a device is attached or not. CSC bit is
> set only after link training completion. We could have used link
> status information, if device would have enabled its pullup soon
^^^^^^^^
Just to clarify, please read pullup here as SS RX Termination.
~Pratyush
> after VBUS ON and then quickly would have moved to polling state. But
> none of these are predictable, as you would have already seen in analyzer
> log of one the device (in the snapshot of last mail) that for a long
> time after VBUS enable device has not enabled pullup.
>
> ~Pratyush
> >
> > David
> >
> >
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