linux-kernel - Re: Missing USB XHCI and EHCI reset for kexec

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Date:	Tue, 15 Apr 2014 15:05:19 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Stefani Seibold <stefani@...bold.net>
cc:	linux-usb <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com>,
	<sarah.a.sharp@...ux.intel.com>, <andreas.brief@...de-schwarz.com>
Subject: Re: Missing USB XHCI and EHCI reset for kexec

On Tue, 15 Apr 2014, Stefani Seibold wrote:

> > One other thing you can try is to increase the reset timeout in 
> > drivers/usb/host/ehci-hub.c.  This is under the USB_PORT_FEAT_RESET 
> > case in ehci_hub_control(), around line 1225:
> > 
> > 				/*
> > 				 * caller must wait, then call GetPortStatus
> > 				 * usb 2.0 spec says 50 ms resets on root
> > 				 */
> > 				ehci->reset_done [wIndex] = jiffies
> > 						+ msecs_to_jiffies (50);
> > 
> > Increasing the 50 to 100 or more might help.
> > 
> > Alan Stern
> > 
> 
> I tried this, when i increase the value to 1000, the reset and
> enumeration process will be faster after a kexec: 28 Seconds vs. 162
> Seconds.

Even 28 seconds is much longer than it should be.  And a 1000-ms long 
reset signal is a lot longer than any device should need.

Anyway, since you saw the same problem after unbind and rebind, you 
don't have to perform a kexec for testing.

Alan Stern

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