FAILED: patch "[PATCH] xhci: dbc: Fix full DbC transfer ring after several" failed to apply to 6.6-stable tree

FAILED: patch "[PATCH] xhci: dbc: Fix full DbC transfer ring after several" failed to apply to 6.6-stable tree

[gregkh]

The patch below does not apply to the 6.6-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-6.6.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 '2025091739-chaste-kilometer-da82@gregkh' --subject-prefix 'PATCH 6.6.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.com
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;
 		}
 

[PATCH 6.6.y 1/2] xhci: dbc: decouple endpoint allocation from initialization

[Sasha Levin]

From: Mathias Nyman <mathias.nyman@linux.intel.com>

[ Upstream commit 220a0ffde02f962c13bc752b01aa570b8c65a37b ]

Decouple allocation of endpoint ring buffer from initialization
of the buffer, and initialization of endpoint context parts from
from the rest of the contexts.

It allows driver to clear up and reinitialize endpoint rings
after disconnect without reallocating everything.

This is a prerequisite for the next patch that prevents the transfer
ring from filling up with cancelled (no-op) TRBs if a debug cable is
reconnected several times without transferring anything.

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/20250902105306.877476-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/host/xhci-dbgcap.c | 71 ++++++++++++++++++++++------------
 1 file changed, 46 insertions(+), 25 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index 2cd8c757c6534..0f921df7a09e4 100644
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -86,13 +86,34 @@ static u32 xhci_dbc_populate_strings(struct dbc_str_descs *strings)
 	return string_length;
 }
 
+static void xhci_dbc_init_ep_contexts(struct xhci_dbc *dbc)
+{
+	struct xhci_ep_ctx      *ep_ctx;
+	unsigned int		max_burst;
+	dma_addr_t		deq;
+
+	max_burst               = DBC_CTRL_MAXBURST(readl(&dbc->regs->control));
+
+	/* Populate bulk out endpoint context: */
+	ep_ctx                  = dbc_bulkout_ctx(dbc);
+	deq                     = dbc_bulkout_enq(dbc);
+	ep_ctx->ep_info         = 0;
+	ep_ctx->ep_info2        = dbc_epctx_info2(BULK_OUT_EP, 1024, max_burst);
+	ep_ctx->deq             = cpu_to_le64(deq | dbc->ring_out->cycle_state);
+
+	/* Populate bulk in endpoint context: */
+	ep_ctx                  = dbc_bulkin_ctx(dbc);
+	deq                     = dbc_bulkin_enq(dbc);
+	ep_ctx->ep_info         = 0;
+	ep_ctx->ep_info2        = dbc_epctx_info2(BULK_IN_EP, 1024, max_burst);
+	ep_ctx->deq             = cpu_to_le64(deq | dbc->ring_in->cycle_state);
+}
+
 static void xhci_dbc_init_contexts(struct xhci_dbc *dbc, u32 string_length)
 {
 	struct dbc_info_context	*info;
-	struct xhci_ep_ctx	*ep_ctx;
 	u32			dev_info;
-	dma_addr_t		deq, dma;
-	unsigned int		max_burst;
+	dma_addr_t		dma;
 
 	if (!dbc)
 		return;
@@ -106,20 +127,8 @@ static void xhci_dbc_init_contexts(struct xhci_dbc *dbc, u32 string_length)
 	info->serial		= cpu_to_le64(dma + DBC_MAX_STRING_LENGTH * 3);
 	info->length		= cpu_to_le32(string_length);
 
-	/* Populate bulk out endpoint context: */
-	ep_ctx			= dbc_bulkout_ctx(dbc);
-	max_burst		= DBC_CTRL_MAXBURST(readl(&dbc->regs->control));
-	deq			= dbc_bulkout_enq(dbc);
-	ep_ctx->ep_info		= 0;
-	ep_ctx->ep_info2	= dbc_epctx_info2(BULK_OUT_EP, 1024, max_burst);
-	ep_ctx->deq		= cpu_to_le64(deq | dbc->ring_out->cycle_state);
-
-	/* Populate bulk in endpoint context: */
-	ep_ctx			= dbc_bulkin_ctx(dbc);
-	deq			= dbc_bulkin_enq(dbc);
-	ep_ctx->ep_info		= 0;
-	ep_ctx->ep_info2	= dbc_epctx_info2(BULK_IN_EP, 1024, max_burst);
-	ep_ctx->deq		= cpu_to_le64(deq | dbc->ring_in->cycle_state);
+	/* Populate bulk in and out endpoint contexts: */
+	xhci_dbc_init_ep_contexts(dbc);
 
 	/* Set DbC context and info registers: */
 	lo_hi_writeq(dbc->ctx->dma, &dbc->regs->dccp);
@@ -421,6 +430,23 @@ dbc_alloc_ctx(struct device *dev, gfp_t flags)
 	return ctx;
 }
 
+static void xhci_dbc_ring_init(struct xhci_ring *ring)
+{
+	struct xhci_segment *seg = ring->first_seg;
+
+	/* clear all trbs on ring in case of old ring */
+	memset(seg->trbs, 0, TRB_SEGMENT_SIZE);
+
+	/* Only event ring does not use link TRB */
+	if (ring->type != TYPE_EVENT) {
+		union xhci_trb *trb = &seg->trbs[TRBS_PER_SEGMENT - 1];
+
+		trb->link.segment_ptr = cpu_to_le64(ring->first_seg->dma);
+		trb->link.control = cpu_to_le32(LINK_TOGGLE | TRB_TYPE(TRB_LINK));
+	}
+	xhci_initialize_ring_info(ring, 1);
+}
+
 static struct xhci_ring *
 xhci_dbc_ring_alloc(struct device *dev, enum xhci_ring_type type, gfp_t flags)
 {
@@ -449,15 +475,10 @@ xhci_dbc_ring_alloc(struct device *dev, enum xhci_ring_type type, gfp_t flags)
 
 	seg->dma = dma;
 
-	/* Only event ring does not use link TRB */
-	if (type != TYPE_EVENT) {
-		union xhci_trb *trb = &seg->trbs[TRBS_PER_SEGMENT - 1];
-
-		trb->link.segment_ptr = cpu_to_le64(dma);
-		trb->link.control = cpu_to_le32(LINK_TOGGLE | TRB_TYPE(TRB_LINK));
-	}
 	INIT_LIST_HEAD(&ring->td_list);
-	xhci_initialize_ring_info(ring, 1);
+
+	xhci_dbc_ring_init(ring);
+
 	return ring;
 dma_fail:
 	kfree(seg);
-- 
2.51.0

[PATCH 6.6.y 2/2] xhci: dbc: Fix full DbC transfer ring after several reconnects

[Sasha Levin]

From: Mathias Nyman <mathias.nyman@linux.intel.com>

[ Upstream commit a5c98e8b1398534ae1feb6e95e2d3ee5215538ed ]

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.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/host/xhci-dbgcap.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index 0f921df7a09e4..764657070883c 100644
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -447,6 +447,25 @@ static void xhci_dbc_ring_init(struct xhci_ring *ring)
 	xhci_initialize_ring_info(ring, 1);
 }
 
+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)
 {
@@ -871,7 +890,7 @@ 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;
 		}
 
@@ -881,7 +900,7 @@ 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;
 		}
 
-- 
2.51.0