1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index b2d654b7477e..54139a2f06ce 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2684,6 +2684,10 @@ static u32 xhci_v1_0_td_remainder(int running_total, int trb_buff_len,
 {
         int packets_transferred;
 
+        /* One TRB with a zero-length data packet. */
+        if (running_total == 0 && trb_buff_len == 0)
+                return 0;
+
         /* All the TRB queueing functions don't count the current TRB in
          * running_total.
          */
@@ -3125,20 +3129,15 @@ static int count_isoc_trbs_needed(struct xhci_hcd *xhci,
                 struct urb *urb, int i)
 {
         int num_trbs = 0;
-        u64 addr, td_len, running_total;
+        u64 addr, td_len;
 
         addr = (u64) (urb->transfer_dma + urb->iso_frame_desc[i].offset);
         td_len = urb->iso_frame_desc[i].length;
 
-        running_total = TRB_MAX_BUFF_SIZE - (addr & (TRB_MAX_BUFF_SIZE - 1));
-        running_total &= TRB_MAX_BUFF_SIZE - 1;
-        if (running_total != 0)
-                num_trbs++;
-
-        while (running_total < td_len) {
+        num_trbs = DIV_ROUND_UP(td_len + (addr & (TRB_MAX_BUFF_SIZE - 1)),
+                        TRB_MAX_BUFF_SIZE);
+        if (num_trbs == 0)
                 num_trbs++;
-                running_total += TRB_MAX_BUFF_SIZE;
-        }
 
         return num_trbs;
 }
@@ -3250,9 +3249,11 @@ static int xhci_queue_isoc_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                 addr = start_addr + urb->iso_frame_desc[i].offset;
                 td_len = urb->iso_frame_desc[i].length;
                 td_remain_len = td_len;
-                /* FIXME: Ignoring zero-length packets, can those happen? */
                 total_packet_count = roundup(td_len,
                                 le16_to_cpu(urb->ep->desc.wMaxPacketSize));
+                /* A zero-length transfer still involves at least one packet. */
+                if (total_packet_count == 0)
+                        total_packet_count++;
                 burst_count = xhci_get_burst_count(xhci, urb->dev, urb,
                                 total_packet_count);
                 residue = xhci_get_last_burst_packet_count(xhci,