Commit 3d4b81ed authored by Sarah Sharp's avatar Sarah Sharp
Browse files

Revert "usb: xhci: Link TRB must not occur within a USB payload burst" 



This reverts commit 35773dac.  It's a
hack that caused regressions in the usb-storage and userspace USB
drivers that use usbfs and libusb.  Commit 70cabb7d992f "xhci 1.0: Limit
arbitrarily-aligned scatter gather." should fix the issues seen with the
ax88179_178a driver on xHCI 1.0 hosts, without causing regressions.

Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org # 3.12
parent 9cf00d91

drivers/usb/host/xhci-ring.c

+2 −52
Original line number Diff line number Diff line
@@ -2967,58 +2967,8 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring, 
	}



	while (1) {

		if (room_on_ring(xhci, ep_ring, num_trbs)) {

			union xhci_trb *trb = ep_ring->enqueue;

			unsigned int usable = ep_ring->enq_seg->trbs +

					TRBS_PER_SEGMENT - 1 - trb;

			u32 nop_cmd;



			/*

			 * Section 4.11.7.1 TD Fragments states that a link

			 * TRB must only occur at the boundary between

			 * data bursts (eg 512 bytes for 480M).

			 * While it is possible to split a large fragment

			 * we don't know the size yet.

			 * Simplest solution is to fill the trb before the

			 * LINK with nop commands.

			 */

			if (num_trbs == 1 || num_trbs <= usable || usable == 0)

				break;



			if (ep_ring->type != TYPE_BULK)

				/*

				 * While isoc transfers might have a buffer that

				 * crosses a 64k boundary it is unlikely.

				 * Since we can't add NOPs without generating

				 * gaps in the traffic just hope it never

				 * happens at the end of the ring.

				 * This could be fixed by writing a LINK TRB

				 * instead of the first NOP - however the

				 * TRB_TYPE_LINK_LE32() calls would all need

				 * changing to check the ring length.

				 */

				break;



			if (num_trbs >= TRBS_PER_SEGMENT) {

				xhci_err(xhci, "Too many fragments %d, max %d\n",

						num_trbs, TRBS_PER_SEGMENT - 1);

				return -ENOMEM;

			}



			nop_cmd = cpu_to_le32(TRB_TYPE(TRB_TR_NOOP) |

					ep_ring->cycle_state);

			ep_ring->num_trbs_free -= usable;

			do {

				trb->generic.field[0] = 0;

				trb->generic.field[1] = 0;

				trb->generic.field[2] = 0;

				trb->generic.field[3] = nop_cmd;

				trb++;

			} while (--usable);

			ep_ring->enqueue = trb;

		if (room_on_ring(xhci, ep_ring, num_trbs))

			break;

		}



		if (ep_ring == xhci->cmd_ring) {

			xhci_err(xhci, "Do not support expand command ring\n");

include/linux/usb.h

+0 −2
Original line number Diff line number Diff line
@@ -1265,8 +1265,6 @@ typedef void (*usb_complete_t)(struct urb *); 
 * @sg: scatter gather buffer list, the buffer size of each element in

 * 	the list (except the last) must be divisible by the endpoint's

 * 	max packet size if no_sg_constraint isn't set in 'struct usb_bus'

 * 	(FIXME: scatter-gather under xHCI is broken for periodic transfers.

 * 	Do not use urb->sg for interrupt endpoints for now, only bulk.)

 * @num_mapped_sgs: (internal) number of mapped sg entries

 * @num_sgs: number of entries in the sg list

 * @transfer_buffer_length: How big is transfer_buffer.  The transfer may

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