Messages in this thread | | | Date | Fri, 19 Jul 2013 11:26:56 -0400 (EDT) | From | Alan Stern <> | Subject | RE: [PATCH] [RFC] EHCI: add to memory barrier to updating hw_next |
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On Fri, 19 Jul 2013, Gioh Kim wrote:
> > I was going to ask the same question. This particular piece of code gets > > executed _only_ when an URB is unlinked. Not during any other kind of > > error. > > > I've got the problem when I listened to the mp3 file of USB HDD. > I checked the urb data when the problem occurred, the last-status value of > urb was EINPROGRESS and > urb->unlinked was ECONNRESET.
Ah, so the URB _was_ unlinked.
> I think the 'stopped' case was occurred by the reset of USB port. > The block device driver did reset USB port because there is no return from > USB device.
Okay.
> If I made block device driver could not reset USB port, the EHCI driver > codes were not executed. > Finally the halt of HC makes 'stopped' case.
Why was the HC halted? That should happen only when there is an extremely severe error.
> I think halt of the HC might be caused that store-buffer delays command for > HC. > When I applied the patch from https://lkml.org/lkml/2011/8/31/344 and added > a mb() into hw_next updating > to remove delay of store-buffer, My platform works well. > > Can the store-buffer delay halt HC? Is it possible?
I don't see how. It could slow things down but it should not cause any errors.
> IMHO, if the qTD list is broken the HC think there is no qTD to send. > So I added mb() at hw_next update code.
At the time when the hw_next update gets executed, what is the value of "state"? It should be QH_STATE_IDLE.
Alan Stern
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