diff options
Diffstat (limited to 'drivers/usb/host/xhci-ring.c')
| -rw-r--r-- | drivers/usb/host/xhci-ring.c | 54 |
1 files changed, 52 insertions, 2 deletions
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 1e2f3f495843..53c2e296467f 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -2973,8 +2973,58 @@ 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 (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"); |