Section 4.11.7.1 of rev 1.0 of the xhci specification states that a link TRB
can only occur at a boundary between underlying USB frames (512 bytes for 480M).
If this isn't done the USB frames aren't formatted correctly and, for example,
the USB3 ethernet ax88179_178a card will stop sending (while still receiving)
when running a netperf tcp transmit test with (say) and 8k buffer.
While this change improves things a lot (it runs for 20 minutes rather than
a few seconds), there is still something else wrong.
This should be a candidate for stable, the ax88179_178a driver defaults to
gso and tso enabled so it passes a lot of fragmented skb to the USB stack.
Signed-off-by: David Laight <david.lai...@aculab.com>
---
Although I've got a USB2 analyser its trigger and trace stuff is almost
unusable! In any case this fails much faster on USB3 (Intel i7 cpu).
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 5480215..23abc9b 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2927,8 +2932,43 @@ static int prepare_ring(struct xhci_hcd *xhci, struct
xhci_ring *ep_ring,
}
while (1) {
- if (room_on_ring(xhci, ep_ring, num_trbs))
- break;
+ 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 (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);
+ for (; !TRB_TYPE_LINK_LE32(trb->link.control); trb++) {
+ trb->generic.field[0] = 0;
+ trb->generic.field[1] = 0;
+ trb->generic.field[2] = 0;
+ trb->generic.field[3] = nop_cmd;
+ ep_ring->num_trbs_free--;
+ }
+ 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");
--
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