linux-kernel - Re: [PATCH 1/1] usb: xhci: apply XHCI_AVOID_BEI quirk to Intel ValleyView and LynxPoint LP

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Date:	Thu, 12 Mar 2015 10:46:31 +0200
From:	Mathias Nyman <mathias.nyman@...ux.intel.com>
To:	Lu Baolu <baolu.lu@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	dheitmueller@...nellabs.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] usb: xhci: apply XHCI_AVOID_BEI quirk to Intel ValleyView
 and LynxPoint LP

On 12.03.2015 03:39, Lu Baolu wrote:
> When a device with an isochronous endpoint is plugged into the Intel
> xHCI host controller, and the driver submits multiple frames per URB,
> the xHCI driver will set the Block Event Interrupt (BEI) flag on all
> but the last TD for the URB. This causes the host controller to place
> an event on the event ring, but not send an interrupt. When the last
> TD for the URB completes, BEI is cleared, and we get an interrupt for
> the whole URB.
> 
> However,  under some Intel xHCI host controllers like ValleyView and
> Lynx Point LP, if the event ring is full of events from transfers with
> BEI set, a "Event Ring is Full" event will be posted to the last entry
> of the event ring, but no interrupt is generated. Host will cease all
> transfer and command executions  and  wait until software completes
> handling the pending events in event ring. That means xHC stops but
> event of "event ring is full" is not notified. As the result, the xHC
> looks like dead to user.
> 
> The patch is to apply XHCI_AVOID_BEI to Intel VallyView and Lynx Point
> LP devices. And it should be backported to kernels as old as 3.0, that
> contains the commit 69e848c2090a ("Intel xhci: Support EHCI/xHCI port
> switching.")
> 

Maybe we should set the quirk for all Intel xHCI controllers.
So far the list includes Pantherpoint, Lynxpoint and valleyview.

I bet it concerns most Intel platforms.

-Mathias



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