On 1/20/26 3:50 PM, ANANDHAKRISHNAN S wrote:
When aborting a Transfer Descriptor (TD), the xHCI driver updates the
device dequeue pointer by converting the virtual enqueue TRB pointer
into a DMA address.
reset_ep() seems to have the same problem ?
Previously, the code OR-ed the ring's Dequeue Cycle State (DCS) bit into
the virtual TRB pointer before passing it to xhci_trb_virt_to_dma().
This produced an unaligned virtual address (e.g. ending in 0x...1).
Inside xhci_trb_virt_to_dma(), the offset calculation:
segment_offset = trb - seg->trbs;
operated on this unaligned pointer, resulting in an incorrect TRB index.
In wraparound cases, this caused the bounds check to fail and the
function to return 0.
As a result, a SET_DEQ_PTR command was issued with a DMA address of 0x0,
leading to controller hangs and transfer timeouts, most commonly when
aborting TDs near the end of a ring segment (e.g. index 63).
Fix this by translating the aligned virtual TRB pointer to a DMA address
first, and only then applying the DCS bit to the resulting physical
address.
Signed-off-by: ANANDHAKRISHNAN S <[email protected]>
---
drivers/usb/host/xhci-ring.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 34eb4536f0e..9e0ff71710a 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -582,9 +582,11 @@ static void abort_td(struct usb_device *udev, int ep_index)
TRB_TO_SLOT_ID(le32_to_cpu(event->event_cmd.flags)) !=
udev->slot_id ||
(comp != COMP_SUCCESS && comp != COMP_CTX_STATE));
xhci_acknowledge_event(ctrl);
-
- addr = xhci_trb_virt_to_dma(ring->enq_seg,
- (void *)((uintptr_t)ring->enqueue | ring->cycle_state));
- (void *)((uintptr_t)ring->enqueue | ring->cycle_state));
+ (void *)(uintptr_t)ring->enqueue) | ring->cycle_state;
cycle_state is already either 0 or 1, isn't it ?
+ addr = xhci_trb_virt_to_dma(ring->enq_seg, ring->enqueue);
+ if (ring->cycle_state)
+ addr |= 0x1ULL;
+ else
+ addr &= ~0x1ULL;
xhci_queue_command(ctrl, addr, udev->slot_id, ep_index, TRB_SET_DEQ);
event = xhci_wait_for_event(ctrl, TRB_COMPLETION);
if (!event)
