From 474ed23a6257b552ab48585c1511eac98653b4e8 Mon Sep 17 00:00:00 2001 From: Mathias Nyman Date: Tue, 21 Jun 2016 10:58:01 +0300 Subject: [PATCH] xhci: align the last trb before link if it is easily splittable. TD fragments section 4.11.7.1 in xhci specs have additional requirements on how trbs in TDs must be organized. TD fragments shall not span transfer ring segments and TD fragments must be packet aligned. Normally we don't care about TD fragments, on TD is one big fragment, but if a TD spans ring segments it will be treated as two fragments, and we need to comply with the alignment requirements. For us this means that the payload data must be packet aligned in the last trb before a link trb. In most mass storage bulk tranfers we are lucky as the block size aligns nicely with packet size, and there are no issues. However, usb network adapters using scatterlists can hit this alignment issue, and usbtest in kernel triggers this in minutes. This patch is a partial solution, it solves the easy case when the last trb before the link trb contains a packet boundary. If that is the case then just split the trb at the boundary. If not, then just print a debug message and continue as we have always done, hoping for the best Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 519dc14a8794..81bb8bfdb7e6 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -3116,6 +3116,27 @@ static u32 xhci_td_remainder(struct xhci_hcd *xhci, int transferred, return (total_packet_count - ((transferred + trb_buff_len) / maxp)); } +static int xhci_align_td(struct xhci_hcd *xhci, struct urb *urb, u32 enqd_len, + u32 *trb_buff_len) +{ + unsigned int unalign; + unsigned int max_pkt; + + max_pkt = GET_MAX_PACKET(usb_endpoint_maxp(&urb->ep->desc)); + unalign = (enqd_len + *trb_buff_len) % max_pkt; + + /* we got lucky, last normal TRB data on segment is packet aligned */ + if (unalign == 0) + return 0; + + /* is the last nornal TRB alignable by splitting it */ + if (*trb_buff_len > unalign) { + *trb_buff_len -= unalign; + return 0; + } + return 1; +} + /* This is very similar to what ehci-q.c qtd_fill() does */ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags, struct urb *urb, int slot_id, unsigned int ep_index) @@ -3198,6 +3219,12 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags, */ if (enqd_len + trb_buff_len < full_len) { field |= TRB_CHAIN; + if (last_trb(xhci, ring, ring->enq_seg, + ring->enqueue + 1)) { + if (xhci_align_td(xhci, urb, enqd_len, + &trb_buff_len)) + xhci_dbg(xhci, "TRB align fail\n"); + } } else { field |= TRB_IOC; more_trbs_coming = false; -- 2.20.1