Re: Re [patch 2/3] fastboot: turn the USB hostcontroller initcallsinto async initcalls

[Simon Arlott]

On 19/07/08 16:25, Alan Stern wrote:
> On 18 July, 2008, Arjan van de Ven wrote:
>
> > From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
> > Subject: [PATCH] fastboot: turn the USB hostcontroller initcalls into 
> > async initcalls
> >
> > the USB host controller init calls take a long time, mostly due to a
> > "minimally 100 msec" delay *per port* during initialization.
> > These are prime candidates for going in parallel to everything else.
> >
> > The USB device ordering is not affected by this due to the
> > serialized-within-eachother property of async initcalls.
>
> Is there some reason this patch wasn't posted to the linux-usb mailing
> list as well as to LKML?
>
> Where is this "minimally 100 msec" per-port delay you refer to?  
> Offhand I can't recall any such delays in the init routines.

usb/core/hub.c:

/* USB 2.0 spec, 7.1.7.3 / fig 7-29:
*
* Between connect detection and reset signaling there must be a delay
* of 100ms at least for debounce and power-settling.  The corresponding
* timer shall restart whenever the downstream port detects a disconnect.
*
* Apparently there are some bluetooth and irda-dongles and a number of
* low-speed devices for which this debounce period may last over a second.
* Not covered by the spec - but easy to deal with.
*
* This implementation uses a 1500ms total debounce timeout; if the
* connection isn't stable by then it returns -ETIMEDOUT.  It checks
* every 25ms for transient disconnects.  When the port status has been
* unchanged for 100ms it returns the port status.
*/

Could it do that for all ports on the hub in parallel instead?

--
Simon Arlott
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