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From: Ross Zwisler <zwisler@google.com>
To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"kernel@collabora.com" <kernel@collabora.com>
Subject: Re: xhci problem -> general protection fault
Date: Tue, 8 Dec 2020 10:24:40 -0700
Message-ID: <X8+22DeNDn1A7X+N@google.com> (raw)
In-Reply-To: <b6eba37b-c78b-fc99-5aca-f9e5856e80ac@linux.intel.com>

On Fri, Dec 04, 2020 at 08:07:30PM +0200, Mathias Nyman wrote:
<>
> Ok, thanks.
> 
> Then the rootcause remains unknown.
> For some reason the endpoint context dequeue pointer field contains zero
> instead of the new dequeue pointer.
> The (output) endpoint context is supposed to be written only by the controller.
> 
> Time to change strategy and start to detect and treat the symptoms instead.
> 
> I wrote a patch that detects the 0-dequeue pointer and issues a
> new Set TR Deq pointer command. Hopefully that works.
> patch added to same branch, can you try it out?
> 
> 3f6326766abc xhci: retry setting new dequeue if xHC hardware failed to update it
> 
> I didn't set a retry limit yet so if it doesn't work it might retry forever.

Here are some logs when running with that commit:

https://gist.github.com/rzwisler/17923c9dedf2b914254eadd1cd294a4c

I think we only consistently get the clean failure case with the dequeue
pointer being 0 if CONFIG_INTEL_IOMMU_DEFAULT_ON=y.

If that option is set to 'n', we get the same failure where the xHCI
controller totally dies (log "CONFIG_INTEL_IOMMU_DEFAULT_ON=n" in the gist).

With CONFIG_INTEL_IOMMU_DEFAULT_ON=y we do seem to live through multiple
errors, but as soon as I try to use the device normally afterwards it seems to
spin forever with these messages:

xhci_hcd 0000:00:14.0: Looking for event-dma 00000000fff0a330 trb-start 00000000f8884000 trb-end 0000000000000000 seg-start 00000000f8884000 seg-end 00000000f8884ff0

Are you able to reproduce this with Andrzej's bulk-cancel script?  I think you
probably just need a device which accepts bulk transfer commands?  In my most
recent reproductions my servo hardware wasn't even attached to a device, so I
don't really think it's doing anything except sitting there and receiving
BULK_IN commands.   I'm doing this to two devices simultaneously.

  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-17 15:30 Andrzej Pietrasiewicz
2020-09-18 10:50 ` Mathias Nyman
2020-09-18 14:20   ` Andrzej Pietrasiewicz
2020-09-25 13:40     ` Mathias Nyman
2020-09-25 21:05       ` Ross Zwisler
2020-09-28 13:32         ` Andrzej Pietrasiewicz
2020-09-29  7:13           ` Mathias Nyman
2020-10-01 14:13             ` Andrzej Pietrasiewicz
2020-09-28 22:35         ` Mathias Nyman
2020-10-01 16:43           ` zwisler
2020-10-12 19:20             ` Mathias Nyman
2020-10-12 21:53               ` zwisler
2020-10-13  7:49                 ` Mathias Nyman
2020-10-13  8:29                   ` Andrzej Pietrasiewicz
2020-10-13 16:44                     ` zwisler
2020-11-19 16:52                   ` Ross Zwisler
2020-11-23 15:06                     ` Mathias Nyman
2020-12-02 22:59                       ` Ross Zwisler
2020-12-04 18:07                         ` Mathias Nyman
2020-12-08 17:24                           ` Ross Zwisler [this message]
2020-12-09 13:11                             ` Mathias Nyman
2020-12-09 18:54                               ` Ross Zwisler
2020-12-30 12:33                                 ` Mathias Nyman
2021-01-06 18:52                                   ` Ross Zwisler
2021-01-07  8:57                                     ` Mathias Nyman
2021-01-07 16:07                                       ` Ross Zwisler

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