On Mon, 25 Jun 2007, Oliver Neukum wrote:

> Am Montag, 25. Juni 2007 schrieb Jiri Kosina:
> > On Fri, 22 Jun 2007, Oliver Neukum wrote:
> > 
> > > could you please run two tests?
> > > 1. set the autosuspend timeout to 0 (this'll kill usb mice)
> > 
> > And it kills also my testing keyboard on the UHCI system. After the 
> > keyboard gets suspended and I hit a key, it wakes up (the LEDs come up), 
> > but no keypressess are produced and the keyboard gets suspended again.
> 
> I had a hunch that UHCI handles remote wakeup incorrectly while the
> hub above the device is still active. This seems to kill that theory.

Setting the timeout to 0 would cause lots of weird things to happen.  
The driver might not even have time to query the device before it gets 
suspended again!

> > > 2. use a 1.1 hub
> > 
> > I grabbed a random HUB (usbhub4c from Linksys) and this made it work 
> > nicely even on UHCI-based system I am testing on.
> > 
> > I will do some more debugging to check what exactly goes wrong, but I am 
> > leaving for OLS tomorrow.
> 
> Is it a 1.1 hub or a 2.0 hub? If the latter you just switch the device
> to ehci. Did you unload ehci_hcd for the test?
> 
> > BTW I don't know if you recall - I reported previously that the keypresses 
> > are lost only if I try to hit the key very soon after the keyboard gets 
> > suspended. If I wait for 2 seconds (looks like exact value), then no 
> > keypressess are lost and the keyboard wakes up properly.
> 
> Alan, is there something in UHCI that uses that 2 second value?

No.

> That indicates that something's wrong in uhci's root hub code.

Could well be.  I'll try duplicating the experiment: suspend the 
keyboard and less than 2 seconds later type some keys.  I don't have 
the HID-autosuspend patch installed, but a manual suspend with remote 
wakeup should work pretty much the same.

Jiri, I'll look for you at OLS.

Alan Stern


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