usb/host/xhci-ring.c

19  * 1. A ring is empty if enqueue == dequeue.  This means there will always be at
22  * 2. When incrementing an enqueue or dequeue pointer, if the next TRB is a
27  * 3. A ring is full if enqueue++ (for the definition of increment above)
33  * 2. When a producer increments an enqueue pointer and encounters a toggle bit
37  * 1. Check if ring is full before you enqueue.
39  *    Update enqueue pointer between each write (which may update the ring
146  * effect the ring dequeue or enqueue pointers.
217  * @more_trbs_coming:	Will you enqueue more TRBs before calling
227 	chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;
229 	if (last_trb_on_seg(ring->enq_seg, ring->enqueue)) {
230 		xhci_err(xhci, "Tried to move enqueue past ring segment\n");
234 	next = ++(ring->enqueue);
243 		 * prepare_ring() just before we enqueue the TD at the top of
268 		ring->enqueue = ring->enq_seg->trbs;
269 		next = ring->enqueue;
281  * Return number of free normal TRBs from enqueue to dequeue pointer on ring.
289 	union xhci_trb *enq = ring->enqueue;
317  * Check to see if there's room to enqueue num_trbs on the ring and make sure
318  * enqueue pointer will not advance into dequeue segment. See rules above.
330 	enq_used = ring->enqueue - ring->enq_seg->trbs;
332 	/* how many trbs will be queued past the enqueue segment? */
344 	/* Empty ring special case, enqueue stuck on link trb while dequeue advanced */
345 	if (trb_is_link(ring->enqueue) && ring->enq_seg->next->trbs == ring->dequeue)
425 	if ((xhci->cmd_ring->dequeue != xhci->cmd_ring->enqueue) &&
662 	 * can move the dequeue pointer to the current enqueue position.
669 			new_deq = ep_ring->enqueue;
671 			xhci_dbg(xhci, "ep ring empty, Set new dequeue = enqueue");
765  * (The last TRB actually points to the ring enqueue pointer, which is not part
1725 	/* If CMD ring stopped we own the trbs between enqueue and dequeue */
3191  * @more_trbs_coming:	Will you enqueue more TRBs before calling
3200 	trb = &ring->enqueue->generic;
3268 	while (trb_is_link(ep_ring->enqueue)) {
3275 			ep_ring->enqueue->link.control &=
3278 			ep_ring->enqueue->link.control |=
3282 		ep_ring->enqueue->link.control ^= cpu_to_le32(TRB_CYCLE);
3285 		if (link_trb_toggles_cycle(ep_ring->enqueue))
3289 		ep_ring->enqueue = ep_ring->enq_seg->trbs;
3298 	if (last_trb_on_seg(ep_ring->enq_seg, ep_ring->enqueue)) {
3350 	td->first_trb = ep_ring->enqueue;
3645 	 * state may change as we enqueue the other TRBs, so save it too.
3647 	start_trb = &ring->enqueue->generic;
3676 			if (trb_is_link(ring->enqueue + 1)) {
3690 			td->last_trb = ring->enqueue;
3740 		urb_priv->td[1].last_trb = ring->enqueue;
3800 	 * state may change as we enqueue the other TRBs, so save it too.
3802 	start_trb = &ep_ring->enqueue->generic;
3867 	td->last_trb = ep_ring->enqueue;
4081 	start_trb = &ep_ring->enqueue->generic;
4158 				td->last_trb = ep_ring->enqueue;
4227 	urb_priv->td[0].last_trb = ep_ring->enqueue;
4231 	/* Reset the ring enqueue back to the first TRB and its cycle bit. */
4232 	ep_ring->enqueue = urb_priv->td[0].first_trb;
4356 	cmd->command_trb = xhci->cmd_ring->enqueue;