USB: xhci: Set transfer descriptor size field correctly.

The transfer descriptor (TD) is a series of transfer request buffers
(TRBs) that describe the buffer pointer, length, and other
characteristics.  The xHCI controllers want to know an estimate of how
long the TD is, for caching reasons.  In each TRB, there is a "TD size"
field that provides a rough estimate of the remaining buffers to be
transmitted, including the buffer pointed to by that TRB.

The TD size is 5 bits long, and contains the remaining size in bytes,
right shifted by 10 bits.  So a remaining TD size less than 1024 would get
a zero in the TD size field, and a remaining size greater than 32767 would
get 31 in the field.

This patches fixes a bug in the TD_REMAINDER macro that is triggered when
the URB has a scatter gather list with a size bigger than 32767 bytes.
Not all host controllers pay attention to the TD size field, so the bug
will not appear on all USB 3.0 hosts.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 24 insertions, 3 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 371ba4297d9c..d7e10ea8f080 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1699,6 +1699,21 @@ int xhci_queue_intr_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         return xhci_queue_bulk_tx(xhci, GFP_ATOMIC, urb, slot_id, ep_index);
 }
 
+/*
+ * The TD size is the number of bytes remaining in the TD (including this TRB),
+ * right shifted by 10.
+ * It must fit in bits 21:17, so it can't be bigger than 31.
+ */
+static u32 xhci_td_remainder(unsigned int remainder)
+{
+        u32 max = (1 << (21 - 17 + 1)) - 1;
+
+        if ((remainder >> 10) >= max)
+                return max << 17;
+        else
+                return (remainder >> 10) << 17;
+}
+
 static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                 struct urb *urb, int slot_id, unsigned int ep_index)
 {
@@ -1756,6 +1771,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         do {
                 u32 field = 0;
                 u32 length_field = 0;
+                u32 remainder = 0;
 
                 /* Don't change the cycle bit of the first TRB until later */
                 if (first_trb)
@@ -1785,8 +1801,10 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                                         (unsigned int) (addr + TRB_MAX_BUFF_SIZE) & ~(TRB_MAX_BUFF_SIZE - 1),
                                         (unsigned int) addr + trb_buff_len);
                 }
+                remainder = xhci_td_remainder(urb->transfer_buffer_length -
+                                running_total) ;
                 length_field = TRB_LEN(trb_buff_len) |
-                        TD_REMAINDER(urb->transfer_buffer_length - running_total) |
+                        remainder |
                         TRB_INTR_TARGET(0);
                 queue_trb(xhci, ep_ring, false,
                                 lower_32_bits(addr),
@@ -1899,6 +1917,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 
         /* Queue the first TRB, even if it's zero-length */
         do {
+                u32 remainder = 0;
                 field = 0;
 
                 /* Don't change the cycle bit of the first TRB until later */
@@ -1917,8 +1936,10 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                         td->last_trb = ep_ring->enqueue;
                         field |= TRB_IOC;
                 }
+                remainder = xhci_td_remainder(urb->transfer_buffer_length -
+                                running_total);
                 length_field = TRB_LEN(trb_buff_len) |
-                        TD_REMAINDER(urb->transfer_buffer_length - running_total) |
+                        remainder |
                         TRB_INTR_TARGET(0);
                 queue_trb(xhci, ep_ring, false,
                                 lower_32_bits(addr),
@@ -2006,7 +2027,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         /* If there's data, queue data TRBs */
         field = 0;
         length_field = TRB_LEN(urb->transfer_buffer_length) |
-                TD_REMAINDER(urb->transfer_buffer_length) |
+                xhci_td_remainder(urb->transfer_buffer_length) |
                 TRB_INTR_TARGET(0);
         if (urb->transfer_buffer_length > 0) {
                 if (setup->bRequestType & USB_DIR_IN)