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[83.28.36.56]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-498010aaceasm52531145e9.12.2026.07.30.04.07.01 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Thu, 30 Jul 2026 04:07:02 -0700 (PDT) Date: Thu, 30 Jul 2026 13:08:14 +0200 From: Michal Pecio To: Bart Nagel Cc: linux-usb@vger.kernel.org, mathias.nyman@intel.com Subject: Re: Regression: webcam freezing since Linux 6.15 Message-ID: <20260730130814.65f7891c.michal.pecio@gmail.com> In-Reply-To: References: <20260723081440.0228c59e.michal.pecio@gmail.com> <20260723081440.0228c59e.michal.pecio@gmail.com> <20260725115956.321185a1.michal.pecio@gmail.com> <20260728003131.085171ee.michal.pecio@gmail.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 29 Jul 2026 12:37:01 -0700, Bart Nagel wrote: > I didn't seem to have the "before" blobs your patch indicates in my > repo and it didn't want to apply where I was (at the first failing > commit) so I went to 6.18.28 and applied your patch there. Sorry, forgot to say that the patch was made for 6.15, but if it works on 6.18 then fine. The alien blob IDs are other (unrelated) patches. > [ 340.443735] xhci_hcd 0000:00:14.0: Miss service interval error for slot 7 ep 2 ep_trb_dma 10aea6260 td_dma 10aea6270, set skip flag > [ 340.443740] xhci_hcd 0000:00:14.0: Event 23 for old TD end DMA 10aea6260 after 7us > [ 340.443743] xhci_hcd 0000:00:14.0: BAILING OUT > [ 340.443858] xhci_hcd 0000:00:14.0: Miss service interval error for slot 7 ep 2 ep_trb_dma 0 td_dma 10aea6270, set skip flag > [ 340.443861] xhci_hcd 0000:00:14.0: Miss service interval error for slot 7 ep 2 ep_trb_dma 0 td_dma 10aea6270, set skip flag > [ 340.444110] xhci_hcd 0000:00:14.0: Found td. Clear skip flag for slot 7 ep 2. As expected, ep_trb_dma points one entry before the first pending TD. The driver would throw out all TDs searching for the one which doesn't exist anymore, but we prevented it and later recovered normally after getting some event (not logged) which pointed to a valid TD. So the fix works, maybe with exception of one edge case (see below). We could potentially use it, or revert the bisected patch (it was only an optimization, maybe nobody will notice), or add a quirk for this particular chipset to ignore ep_trb_dma in Missed Service Errors. Long term solution would be improving detection of events pointing to completed TDs and/or not skipping when we don't have a sensible TRB pointer. But we also need a "trivial" fix for stable kernels like 6.18. > Missed service interval messages do not always lead to a "bailing out" > message, like this example: These examples are not interesting because ep_trb_dma is zero. But we know that it can be non-zero and the driver still works (sometimes). I'm slightly curious what exactly happens there (probably MSE after Short Packet on a single-TRB TD), and whether Missed Service Error may point at a Link TRB, because the current fix wouldn't handle that and the stream could still hang. So your failure rate may actually be reduced to 1/255 of what it was, but still not zero. If possible, please boot the patched kernel again and run it for a little longer. If it fails, post dmesg starting from the "Miss service interval error" line which is followed by "All TDs skipped". And while that is running, also collect another log: cd /sys/kernel/tracing/ echo 1 > events/xhci-hcd/xhci_handle_event/enable echo 1 > tracing_on grep -B5 Missed trace_pipe | tee /tmp/trace This is supposed to log 6 lines for every Missed Service Error, so it will grow, but not terribly fast. Regards, Michal