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

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Date:	Sat, 7 Jun 2014 11:40:15 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>,
	linux-usb <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...el.com>
Subject: Re: Missing USB XHCI and EHCI reset for kexec

[Added Mathias  to CC: list]

On Sat, 7 Jun 2014, Benjamin Herrenschmidt wrote:

> I'm trying to kexec from our OPAL FW bootloader (3.10.23 based) to a
> fedora 3.14.3 on a new machine and am still seeing the above.
> 
> A reset brings the chip back.
> 
> Do we have any resolution here ? It looks like the xHCI remains active
> on the way out and is clagged up on the way back in, at least in a
> state the driver really doesn't like.
> 
> And this is a "clean" kexec, not a forced one... This is killing USB on
> the upcoming OpenPower dev machines.

The current xhci-hcd driver includes a quirk flag (XHCI_SPURIOS_WAKEUP) 
that causes the shutdown routine to reset the controller.  It wasn't 
meant for fixing kexec problems, but I bet you could use it for that 
purpose.

In addition, it's possible that a reset is needed in the probe pathway.

Alan Stern

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