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

From: Alan Stern
Date: Sat Jul 19 2008 - 16:36:08 EST

On Sat, 19 Jul 2008, Simon Arlott wrote:

> usb/core/hub.c:
> /* USB 2.0 spec, / 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?

In fact it will, to a large extent. The new code isn't present in
2.6.26 but it ought to be in 2.6.27-rc1.

However Arjan wasn't talking about debounce delays; he was talking
about port-power-on delays. A nice improvement would be to combine the
two types of delay into one. I'll look into it...

Alan Stern

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