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 16:47:19 +0800
From:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
To:	Mathias Nyman <mathias.nyman@...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 03/12/2015 04:46 PM, Mathias Nyman wrote:
> 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.

Yes, I agree with you.

I will send out a new patch for this.

>
> -Mathias
>
>
>
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