The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x a5c98e8b1398534ae1feb6e95e2d3ee5215538ed # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025091734-scouts-eligible-d693@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From a5c98e8b1398534ae1feb6e95e2d3ee5215538ed Mon Sep 17 00:00:00 2001 From: Mathias Nyman mathias.nyman@linux.intel.com Date: Tue, 2 Sep 2025 13:53:05 +0300 Subject: [PATCH] xhci: dbc: Fix full DbC transfer ring after several reconnects
Pending requests will be flushed on disconnect, and the corresponding TRBs will be turned into No-op TRBs, which are ignored by the xHC controller once it starts processing the ring.
If the USB debug cable repeatedly disconnects before ring is started then the ring will eventually be filled with No-op TRBs. No new transfers can be queued when the ring is full, and driver will print the following error message:
"xhci_hcd 0000:00:14.0: failed to queue trbs"
This is a normal case for 'in' transfers where TRBs are always enqueued in advance, ready to take on incoming data. If no data arrives, and device is disconnected, then ring dequeue will remain at beginning of the ring while enqueue points to first free TRB after last cancelled No-op TRB. s Solve this by reinitializing the rings when the debug cable disconnects and DbC is leaving the configured state. Clear the whole ring buffer and set enqueue and dequeue to the beginning of ring, and set cycle bit to its initial state.
Cc: stable@vger.kernel.org Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver") Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Link: https://lore.kernel.org/r/20250902105306.877476-3-mathias.nyman@linux.intel.... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c index d0faff233e3e..63edf2d8f245 100644 --- a/drivers/usb/host/xhci-dbgcap.c +++ b/drivers/usb/host/xhci-dbgcap.c @@ -462,6 +462,25 @@ static void xhci_dbc_ring_init(struct xhci_ring *ring) xhci_initialize_ring_info(ring); }
+static int xhci_dbc_reinit_ep_rings(struct xhci_dbc *dbc) +{ + struct xhci_ring *in_ring = dbc->eps[BULK_IN].ring; + struct xhci_ring *out_ring = dbc->eps[BULK_OUT].ring; + + if (!in_ring || !out_ring || !dbc->ctx) { + dev_warn(dbc->dev, "Can't re-init unallocated endpoints\n"); + return -ENODEV; + } + + xhci_dbc_ring_init(in_ring); + xhci_dbc_ring_init(out_ring); + + /* set ep context enqueue, dequeue, and cycle to initial values */ + xhci_dbc_init_ep_contexts(dbc); + + return 0; +} + static struct xhci_ring * xhci_dbc_ring_alloc(struct device *dev, enum xhci_ring_type type, gfp_t flags) { @@ -885,7 +904,7 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc) dev_info(dbc->dev, "DbC cable unplugged\n"); dbc->state = DS_ENABLED; xhci_dbc_flush_requests(dbc); - + xhci_dbc_reinit_ep_rings(dbc); return EVT_DISC; }
@@ -895,7 +914,7 @@ static enum evtreturn xhci_dbc_do_handle_events(struct xhci_dbc *dbc) writel(portsc, &dbc->regs->portsc); dbc->state = DS_ENABLED; xhci_dbc_flush_requests(dbc); - + xhci_dbc_reinit_ep_rings(dbc); return EVT_DISC; }