xhci: rework cycle bit checking for new dequeue pointers

When we manually need to move the TR dequeue pointer we need to set the
correct cycle bit as well. Previously we used the trb pointer from the
last event received as a base, but this was changed in
commit 1f81b6d22a59 ("usb: xhci: Prefer endpoint context dequeue pointer")
to use the dequeue pointer from the endpoint context instead

It turns out some Asmedia controllers advance the dequeue pointer
stored in the endpoint context past the event triggering TRB, and
this messed up the way the cycle bit was calculated.

Instead of adding a quirk or complicating the already hard to follow cycle bit
code, the whole cycle bit calculation is now simplified and adapted to handle
event and endpoint context dequeue pointer differences.

Fixes: 1f81b6d22a59 ("usb: xhci: Prefer endpoint context dequeue pointer")
Reported-by: Maciej Puzio <mx34567@gmail.com>
Reported-by: Evan Langlois <uudruid74@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Maciej Puzio <mx34567@gmail.com>
Tested-by: Evan Langlois <uudruid74@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-ring.c

@@ -364,32 +364,6 @@ static void ring_doorbell_for_active_rings(struct xhci_hcd *xhci,
 	}
 }
 
-/*
- * Find the segment that trb is in.  Start searching in start_seg.
- * If we must move past a segment that has a link TRB with a toggle cycle state
- * bit set, then we will toggle the value pointed at by cycle_state.
- */
-static struct xhci_segment *find_trb_seg(
-		struct xhci_segment *start_seg,
-		union xhci_trb	*trb, int *cycle_state)
-{
-	struct xhci_segment *cur_seg = start_seg;
-	struct xhci_generic_trb *generic_trb;
-
-	while (cur_seg->trbs > trb ||
-			&cur_seg->trbs[TRBS_PER_SEGMENT - 1] < trb) {
-		generic_trb = &cur_seg->trbs[TRBS_PER_SEGMENT - 1].generic;
-		if (generic_trb->field[3] & cpu_to_le32(LINK_TOGGLE))
-			*cycle_state ^= 0x1;
-		cur_seg = cur_seg->next;
-		if (cur_seg == start_seg)
-			/* Looped over the entire list.  Oops! */
-			return NULL;
-	}
-	return cur_seg;
-}
-
-
 static struct xhci_ring *xhci_triad_to_transfer_ring(struct xhci_hcd *xhci,
 		unsigned int slot_id, unsigned int ep_index,
 		unsigned int stream_id)
@@ -459,9 +433,12 @@ void xhci_find_new_dequeue_state(struct xhci_hcd *xhci,
 	struct xhci_virt_device *dev = xhci->devs[slot_id];
 	struct xhci_virt_ep *ep = &dev->eps[ep_index];
 	struct xhci_ring *ep_ring;
-	struct xhci_generic_trb *trb;
+	struct xhci_segment *new_seg;
+	union xhci_trb *new_deq;
 	dma_addr_t addr;
 	u64 hw_dequeue;
+	bool cycle_found = false;
+	bool td_last_trb_found = false;
 
 	ep_ring = xhci_triad_to_transfer_ring(xhci, slot_id,
 			ep_index, stream_id);
@@ -486,45 +463,45 @@ void xhci_find_new_dequeue_state(struct xhci_hcd *xhci,
 		hw_dequeue = le64_to_cpu(ep_ctx->deq);
 	}
 
-	/* Find virtual address and segment of hardware dequeue pointer */
-	state->new_deq_seg = ep_ring->deq_seg;
-	state->new_deq_ptr = ep_ring->dequeue;
-	while (xhci_trb_virt_to_dma(state->new_deq_seg, state->new_deq_ptr)
-			!= (dma_addr_t)(hw_dequeue & ~0xf)) {
-		next_trb(xhci, ep_ring, &state->new_deq_seg,
-					&state->new_deq_ptr);
-		if (state->new_deq_ptr == ep_ring->dequeue) {
-			WARN_ON(1);
-			return;
-		}
-	}
+	new_seg = ep_ring->deq_seg;
+	new_deq = ep_ring->dequeue;
+	state->new_cycle_state = hw_dequeue & 0x1;
+
 	/*
-	 * Find cycle state for last_trb, starting at old cycle state of
-	 * hw_dequeue. If there is only one segment ring, find_trb_seg() will
-	 * return immediately and cannot toggle the cycle state if this search
-	 * wraps around, so add one more toggle manually in that case.
+	 * We want to find the pointer, segment and cycle state of the new trb
+	 * (the one after current TD's last_trb). We know the cycle state at
+	 * hw_dequeue, so walk the ring until both hw_dequeue and last_trb are
+	 * found.
 	 */
-	state->new_cycle_state = hw_dequeue & 0x1;
-	if (ep_ring->first_seg == ep_ring->first_seg->next &&
-			cur_td->last_trb < state->new_deq_ptr)
-		state->new_cycle_state ^= 0x1;
+	do {
+		if (!cycle_found && xhci_trb_virt_to_dma(new_seg, new_deq)
+		    == (dma_addr_t)(hw_dequeue & ~0xf)) {
+			cycle_found = true;
+			if (td_last_trb_found)
+				break;
+		}
+		if (new_deq == cur_td->last_trb)
+			td_last_trb_found = true;
 
-	state->new_deq_ptr = cur_td->last_trb;
-	xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
-			"Finding segment containing last TRB in TD.");
-	state->new_deq_seg = find_trb_seg(state->new_deq_seg,
-			state->new_deq_ptr, &state->new_cycle_state);
-	if (!state->new_deq_seg) {
-		WARN_ON(1);
-		return;
-	}
+		if (cycle_found &&
+		    TRB_TYPE_LINK_LE32(new_deq->generic.field[3]) &&
+		    new_deq->generic.field[3] & cpu_to_le32(LINK_TOGGLE))
+			state->new_cycle_state ^= 0x1;
+
+		next_trb(xhci, ep_ring, &new_seg, &new_deq);
+
+		/* Search wrapped around, bail out */
+		if (new_deq == ep->ring->dequeue) {
+			xhci_err(xhci, "Error: Failed finding new dequeue state\n");
+			state->new_deq_seg = NULL;
+			state->new_deq_ptr = NULL;
+			return;
+		}
+
+	} while (!cycle_found || !td_last_trb_found);
 
-	/* Increment to find next TRB after last_trb. Cycle if appropriate. */
-	trb = &state->new_deq_ptr->generic;
-	if (TRB_TYPE_LINK_LE32(trb->field[3]) &&
-	    (trb->field[3] & cpu_to_le32(LINK_TOGGLE)))
-		state->new_cycle_state ^= 0x1;
-	next_trb(xhci, ep_ring, &state->new_deq_seg, &state->new_deq_ptr);
+	state->new_deq_seg = new_seg;
+	state->new_deq_ptr = new_deq;
 
 	/* Don't update the ring cycle state for the producer (us). */
 	xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,

drivers/usb/host/xhci.c

@@ -2880,6 +2880,9 @@ void xhci_cleanup_stalled_ring(struct xhci_hcd *xhci,
 			ep_index, ep->stopped_stream, ep->stopped_td,
 			&deq_state);
 
+	if (!deq_state.new_deq_ptr || !deq_state.new_deq_seg)
+		return;
+
 	/* HW with the reset endpoint quirk will use the saved dequeue state to
 	 * issue a configure endpoint command later.
 	 */