Re: Re [patch 2/3] fastboot: turn the USB hostcontroller initcallsinto async initcalls
From: Simon Arlott
Date: Sat Jul 19 2008 - 11:32:36 EST
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
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 2.0 spec, 22.214.171.124 / 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?
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